IC-NRLF 
 
PRESETTED TO THE LIBRARY 
 
 OF THE 
 
 UNIVERSITY 
 
 OF 
 
 CALIFORNIA 
 
 WITH THE COMPLEMENTS 
 OF THE 
 
 PUBLISHER 
 
LABORATORY MANUAL 
 
 OF 
 
 ELECTROTHERAPEUTICS 
 
 BY 
 
 WILLIAM JAMES HERDMAN, Pn. B., M. D.. 
 
 PROFESSOR OF DISEASES OF THE NERVOUS SYSTEM AND ELECT R Or 
 THERAPEUTICS, UNIVERSITY OF MICHIGAN. 
 
 AND 
 
 FRANK W. NAGLER, B.S., 
 
 INSTRUCTOR IN ELECTROTHERAPEUTICS 
 UNIVERSITY OF MICHIGAN. 
 
 GEORGE WAHR, PUBLISHER, 
 ANN ARBOR, MICH. 
 
A- 
 
 COPYRIGHT, 1898 
 GEORGE WAHR 
 
PREFACE. 
 
 For a number of years the opportunity has been given 
 the students in the Department of Medicine and Surgery 
 of the University of Michigan to learn the relation which 
 electricity bears to physiological action and the rational 
 application of that action to therapeutics. 
 
 For some years attendance upon the course of instruc- 
 tion offered in this branch was optional with the student. 
 But so great has been-the accumulation of knowledge con- 
 cerning the part electricity plays in the movements of both 
 animate and inanimate things, and so important a part is 
 it found to take in determining these movements that it 
 can no longer be excluded from a curriculum of study for 
 medical students that aims to be thorough and complete. 
 
 In the study of influences which affect the animal 
 economy, beneficially or otherwise, it is quite as essential 
 that we know the part due to electric action as to know 
 what is due to chemism or to radiant energy in the form of 
 light and heat. 
 
 It has been our experience that the knowledge required 
 by the student of medicine concerning electricity and its 
 relation to animal economy is best acquired by the labora- 
 tory method. By that method of instruction each princi- 
 ple is impressed upon the mind through several separate 
 paths of the sense perception and a manual dexterity is 
 acquired which is essential to success in therapeutic appli- 
 cations. 
 
 This has been the plan adopted for teaching electro- 
 therapeutics at the University of Michigan. Every form 
 
 i: 
 
ERRATA. 
 
 Page 23 line 26 for <4$S$" read 
 " 26 " 2 omit "or". 
 
 pr 
 " 26 " 13 for "C ~^r R" write C = 
 
 n n n 
 
 1 ' in ti in T 
 
 " 26 " 18 for R." write = R - 
 
 n n 
 
 " 43 " 26 for "experiment" write experimental. 
 
 " 50 problem 27 insert R =. 2000. 
 
 " 72 line 4 for "floating" write placing. 
 
 " 97 " 26 for "no direct" write no volt direct. 
 
 " 102 " 4 for "wire" write iron. 
 
 " 105 " 13 for "arrangements" write arrangement. 
 
 "126 " 23 for "from the" write from or. 
 
MEASUREMENT OF THE DIRECT CURRENT. 
 
 The Laboratory Milliamperemeter. The ability 
 to understand the working principles and to use intelli- 
 gently some form of galvanometer is absolutely essential 
 to the student of current electricity. A very simple instru- 
 ment in the hands of a skillful operator can be made to 
 
 yield comparatively accurate re- 
 sults. The instrument used in 
 this laboratory (Fig. i ) is adapt- 
 ed by construction to carry cur- 
 rents which are best expressed, 
 as thousandths of an ampere or 
 "milliamperes;" such an instru- 
 ment is called a milliampereme- 
 ter. This laboratory milliam- 
 peremeter consists of an ordinary compass needle mounted 
 in a block of wood with the wire coils beneath the needle. 
 The coils are wound in form like the figure 8, the part 
 between the binding posts being straight and the return, 
 which is a semi-circle is made first on one side and then 
 on the other. When the instrument is properly placed the 
 the straight part of the coil lies below and parallel to the 
 magnetic needle. When the "A" terminals are employed 
 the current passes eight times below the needle, with the 
 " B " terminals it passes forty times below it. 
 
 The fundamental phenomenon upon which the con- 
 struction of this galvanometer form of milliamperemeter 
 depends is as follows; 
 
 Fig 1. 
 
2 LABORATORY MANUAL 
 
 A freely suspended magnetic needle tends to place itself 
 at right angles to a wire through which a current of elec- 
 tricity is flowing. 
 
 This instrument may be used: 
 
 ist, To detect the presence of a current; 
 
 2d, To determine the direction of a current; 
 
 3d, To determine strength of current; 
 
 4th, To measure electric resistances; 
 
 5th, To measure and compare electro-motive forces, 
 etc. 
 
 This is a modified tangent galvanometer and for 
 deflections not exceeding 10 or 15 the currents are 
 nearly proportional to the deflection. The calibration of 
 one of these instruments gave the following table which 
 shows the current strength in milliamperes corresponding 
 to a given deflection both for the A and B terminals. 
 This table may be used for all instruments of this particu- 
 lar construction, but better results in practical work are 
 obtained if a calibration table is prepared for each instru- 
 ment. Each galvanometer should be carefully examined 
 to see whether the needle swings freely. If this is the 
 case it will come to rest in exactly the same position after 
 every deflection if the instrument has not been moved. 
 
 Throughout the following experiments in which elec- 
 tric currents are to be measured, or compared, it will be 
 necessary to so regulate the battery power as to keep the 
 deflection within the limits for which the instrument is 
 calibrated. 
 
OF ELECTROTHERAPEUTICS. 
 GALVANOMETER CALIBRATION TABLE. 
 
 
 CURRENT IN 
 
 
 CURRENT IN 
 
 
 CURRENT IN 
 
 w" 
 
 MlLLIAMPERES. 
 
 W 
 
 W 
 
 MA. 
 
 in 
 
 W 
 
 MA. 
 
 M 
 
 
 W 
 
 
 W 
 
 
 
 
 
 
 erf 
 
 
 
 
 
 
 o 
 
 
 
 O 
 
 
 
 u 
 
 Q 
 
 A Term. 
 
 B Term. 
 
 w 
 Q 
 
 A Term. 
 
 B Term. 
 
 W 
 
 Q 
 
 A Term. 
 
 B Term. 
 
 jO 
 
 i-5 
 
 25 
 
 11 
 
 21.2 
 
 5.65 
 
 21 
 
 55-9 
 
 14-94 
 
 2 
 
 3- 
 
 52 
 
 12 
 
 23.8 
 
 6.48 
 
 22 
 
 61. 
 
 15-95 
 
 3 
 
 4-5 
 
 9 
 
 13 
 
 26.5 
 
 7-3 
 
 23 
 
 67. 
 
 16.97 
 
 4 
 
 6-3 
 
 1.32 
 
 14 
 
 29.5 
 
 8.2 
 
 24 
 
 73-1 
 
 18. 
 
 5 
 
 8. 
 
 1.8 
 
 15 
 
 32.6 
 
 9.08 
 
 25 
 
 79-3 
 
 
 6 
 
 10. 
 
 2-3 
 
 16 
 
 35-8 
 
 10 
 
 26 
 
 86.2 
 
 
 7 
 
 12. I 
 
 2-9 
 
 17 
 
 39-i 
 
 10.9 
 
 27 
 
 94. 
 
 
 8 
 
 J4-3 
 
 3-54 
 
 18 
 
 42-7 
 
 II. "91 
 
 28 
 
 102.2 
 
 
 9 
 
 16.4 
 
 4.2 
 
 I 9 
 
 46.8 
 
 12.93 
 
 29 
 
 110.8 
 
 
 10 
 
 18.7 
 
 4-9 
 
 20 
 
 5L2 
 
 13.93 
 
 30 
 
 120.0 
 
 
 Fig. 2. The Ordinary form of Milliainperemeter. 
 
EXPERIMENTS WITH CURRENT STRENGTH. 
 
 The Voltaic or Galvanic Cell (T. 168) A com- 
 mon and convenient method for generating a current of 
 electricity is to make use of a glass or porcelain cup, con- 
 taining a liquid, as acidulated water, in which two pieces 
 of dissimilar metals are partially immersed. If to the 
 upper extremities of these strips of metal, wires are at- 
 tached and the opposite ends of the wires are connected 
 to the binding posts of* a galvanometer, the deflection of 
 the galvanometer needle will give evidence that a current 
 of electricity is flowing along the wires. The origin of the 
 electricity in this case is due to the chemical action that is 
 taking place between the acidulated water and one of the 
 metal strips, and is at the expense of that metal since it is 
 gradually consumed. This is a transformation of chemi- 
 cal energy into electrical energy. The cup and contained 
 liquid and metals is called a voltaic or galvanic cell. 
 
 EXPERIMENT i. Take the small strips of copper and 
 zinc furnished. Attach about two feet of copper wire to 
 each strip and attach the other ends of the wires to the ter- 
 minals of the galvanometer 
 marked B in fig. 3. The 
 most sensitive coil of the gal- 
 vanometer is attached to the 
 
 B terminals, and for this reason they should always be used 
 in measuring or testing for the presence of weak currents. 
 Place the galvanometer so that its needle shall point to zero 
 and swing clear of the dial. Immerse the strips in a glass 
 of distilled water, being careful that the strips do not touch, 
 and notice whether the galvanometer needle is deflected. 
 
OF ELECTROTHERAPEUTICS. 5 
 
 If it is, it indicates that a current of electricity has been 
 generated and that there is a difference of electric poten- 
 tial between the copper and zinc. 
 
 EXPERIMENT 2. Using different metals and a glass of 
 hydrant water make the following combination, and test as 
 in the preceding experiment. Note the deflection given 
 in each case and determine which combination gives the 
 greatest deflection, in other words the strongest current. 
 The connections must be bright, the wires tightly fastened 
 and the metal strips must be kept the same distance apart 
 throughout the experiment. It will be found convenient 
 to prepare a strip-holder from a small block of wood and 
 pieces of brass, that are provided, to facilitate the fasten- 
 ings of the plates and wires. Tabulate the results obtained 
 as follows: 
 
 
 Def. 
 
 Cu C 
 
 .. Def 
 
 
 < i 
 
 " Sn 
 
 
 
 (( 
 
 " Fe 
 
 tt 
 
 
 tt 
 
 " Pb 
 
 tt 
 
 
 tt 
 
 " Brass 
 
 (( 
 
 ss 
 
 tt 
 
 _Gal Fe 
 
 n 
 
 . Fe .. 
 
 
 
 
 c^ 
 
 " Sn 
 "- Fe 
 " Pb 
 " Brass 
 
 EXPERIMENT 3. Repeat the preceding experiment 
 using dilute sulphuric acid (H 2 SO 4 ) (1:20) and common 
 salt (NaCl) solution as exciting liquids. Use the A termi- 
 nals of the galvanometer and put a resistance of from 10 
 to 25 ohms* in circuit. Make at least ten more combina- 
 tions than are indicated in EXP. 2, and in each case take 
 three readings. 
 
 1. First swing of the needle. 
 
 2. The permanent deflection. 
 
 3. The permanent deflection after three minutes. 
 * These resistances will be found on the side- table. 
 
6 LABORATORY MANUAL 
 
 Note in each case which metal is electropositive (-J-) 
 and carefully arrange the results in a series in the order of 
 the greatest first swing of the galvanometer needle. The 
 order of the metals in the zinc series and copper series 
 should correspond. It will be found convenient always to 
 attach the zinc to the north and copper to the south termi- 
 nal of the galvanometer. In the properly arranged series 
 each metal, beginning with zinc, will be electropositive (4- ) 
 with respect to the one next below it. 
 
 EXPERIMENT 4. Into some dilute sulphuric acid 
 (H 2 SO 4 ) ( i : 20) place a strip of commercial zinc (Zn) and 
 notice the result. Collect some of the gas given off in a 
 test tube and determine what it is. What would you ob- 
 serve if you were to prepare the dilute acid ? After the 
 liquid has become clear replace the commercial zinc by a 
 piece of chemically pure zinc and note the result (T. 172). 
 The pure zinc should be carefully polished with sand paper 
 to remove all traces of foreign metals and oxidation on its 
 surface. 
 
 EXPERIMENT 5. Amalgamate (see page 21) the com- 
 mercial zinc (Zn) (T. 174). Notice its physical changes 
 and try to bend it at one corner. Immerse it again in the 
 acidulated water and compare the results with those in 
 EXP. 4. 
 
 EXPERIMENT 6. Place a strip of copper in the dilute 
 acid and notice if there is chemical action as in the case 
 of the zinc. 
 
 EXPERIMENT 7. Place the amalgamated zinc and 
 copper strips in dilute acid, being careful that they do not 
 touch each other. How do the results compare with those 
 in EXP'S 5 and 6 (T. 173, 174)? 
 
 EXPERIMENT 8. Allow the metals to come in contact 
 beneath the surface of the liquid. From which plate does 
 
OF ELECTROTHERAPEUTICS. 7 
 
 the gas arise? Is it the same as in EXP. 4? Connect the 
 ends projecting above the liquid by a wire. Notice that 
 the result is the same as before. Now break the connec- 
 tion, what does the result indicate? With the wires con- 
 nected as before what would be the effect of putting a glass 
 partition in the retaining vessel between the two plates? 
 EXPERIMENT 9. Connect the wires to the A terminals 
 of the galvanometer and put in circuit from 10 to 20 ohms 
 resistance. When the needle rests at zero immerse the 
 plates in the fluid and take the reading. Allow the cur- 
 rent to flow 5 minutes and note the deflection every half 
 minute. In this way determine what combination of metals 
 and fluid gives the strongest and most uniform current. 
 Make the following and a few other combinations: 
 
 ( HNO (1:20) 
 (HSO.(i:io)* r or > / 
 
 Cu & Zn CSOSol^ C & Zn ^^Ld 
 
 (NH.GlSol. [NH 4 ClSol. 
 
 Pb and Zn with H 2 SO 4 (1:10) and others. 
 
 EXPERIMENT 10. Take two dissimilar metals, place 
 one above the tongue and the other beneath it and then 
 bring the ends in contact. Observe the peculiar sensa- 
 tion. Try several combinations, noticing what relation 
 the intensity of sensation bears to the deflection of the 
 galvanometer needle obtained with the same pairs of 
 metals. What does this experiment demonstrate? 
 
 The tongue test is a convenient method for detecting 
 weak currents and for currents of short duration. By 
 practice the experimenter can approximately estimate elec- 
 tro-motive forces as high as 10 volts without danger or 
 discomfort. The student should also familiarize himself 
 
 * These solutions will be found on the side table. Fill the glass to 
 the depth of 2 inches in each case. 
 
LABORATORY MANUAL 
 
 with the difference in sensation caused by the positive (-f-) 
 and negative ( ) terminals and thus be able to determine 
 by this means the direction in which a current is flowing 
 along a given wire. 
 
 EXPERIMENT n. Place a tumbler containing fresh 
 bichromate solution fy inch deep over your galvanometer 
 dial. In this, place a narrow strip of amalgamated zinc 
 over the north-seeking end of the needle and a carbon 
 plate over the south-seeking end. Touch the upper ends 
 of the strips together and observe the needle. It 
 may be necessary to use a thin glass beaker and to alter- 
 nately open and close the circuit to get a noticeable effect. 
 What relation does this experiment bear to the preced- 
 ing? What do the two experiments prove concerning a 
 battery ? 
 
 EXPERIMENT 12. The Volta Pile. Construct a 
 Volta pile (T. 164) using n plates each of copper and 
 zinc separated by squares of blotting paper moistened 
 
 Cu, 
 
 -TTZ. 
 
 
 
 
 j- 
 
 Cit, 
 
 Fig. 4. 
 
 with a dilute acetic acid solution. (Strong NaCl solution 
 or any weak acid solution would answer). The squares of 
 paper should be just the size of the plates and should be 
 moistened before setting up the pile. Arrange the plates in 
 the order indicated by the diagram (Fig. 4), soldering wires 
 to the terminal plates and fastening the whole together with 
 a rubber band. With the least possible delay have its 
 voltage measured on the voltmeter, being careful that you 
 have made the proper connection before closing the circuit 
 
6fr ELECTROTHERAPEUTICS. 9 
 
 through the instrument. Bring the wires into contact with 
 your tongue and compare the sensation with that you 
 experience in EXP. 10. Attach the wires to the A termin- 
 als of the galvanometer with a resistance the same as you 
 used in the Zn, Cu and NaCl combination and compare 
 results. 
 
 The volta pile, in some form, has been called upon 
 to do duty in the construction of that innumerable variety 
 of ' ' body batteries " which are sold under the names of 
 'Electric Belts," "Electric Plasters," "Electric Shoe 
 Soles," etc., when there is any pretence in these objection- 
 able devices to generate any current whatever, for often 
 the word " electric " is simply employed as a catch-penny 
 name and has no other reason for its application to the 
 thing so named. 
 
 Many of the electric belts and other such appliances 
 are capable of generating a current of considerable 
 strength so that when used by those ignorant of the action 
 of electricity or of the proper treatment of disease by it, 
 they seldom do good and often do great harm. 
 
 Soldering. A soldering fluid is prepared by dissolv- 
 ing scraps of zinc in hydrochloric acid (HC1) till no more 
 zinc is dissolved. The parts to be united must be scraped 
 clean and bright, and care must be taken to keep them so. 
 Now apply some of the soldering fluid to the surface of 
 the metals, place a small piece of solder between them 
 and apply heat either with a soldering iron or by holding 
 the parts in the flame of a Bunsen burner, being careful to 
 remove them as soon as the solder is melted, and keep 
 them in position till it cools. Should the solder not 
 spread out and adhere intimately to all the parts the 
 process should be repeated. 
 
BATTERY POLARIZATION. 
 
 (T. i75, 176.) 
 
 Construct a Volta cell (T. 166), using plates 1^x3 
 inches. Use the same plate holder that you used in EXP. 
 2, being careful that the metallic parts do not touch 
 and thus "short circuit" the cell. Amalgamate only the 
 the lower three-fourths of the zinc to prevent its breaking, 
 and be sure that all metallic connections are bright and 
 tight. 
 
 EXPERIMENT 13. Connect the terminals of your cell 
 to the A terminals of the galvanometer, having in circuit a 
 resistance of at least 10 ohms. When the needle comes to 
 rest immerse the elements in the dilute acid. Notice that 
 the angle of deflection diminishes rapidly for a time and 
 then more slowly. Allow the cell to continue in action for 
 ten minutes and then jar or brush the gas from the upper 
 plate, noticing the effect on the needle. Repeat, keeping 
 the plates constantly in motion. In each case take the 
 galvanometer reading every half minute and tabulate the 
 results. 
 
 EXPERIMENT 14. Replace the dilute acid of EXP. 
 13 by bichromate solution (K 2 Cr 2 O 7 + H 2 SO 4 + H 2 O). 
 Allow the. cell to continue in action ten minutes and then 
 compare the deflections of the needle with those of the 
 preceding experiment. 
 
 EXPERIMENT 15. Again replace the bichromate solu- 
 tion of EXP. 14 by a solution of copper sulphate (Cu SO 4 ). 
 Allow the cell to act ten minutes, take half-minute readings 
 and compare them with those of EXP'S 13 and 14. 
 
OF ELECTROTHERAPEUTICS. II 
 
 EXPERIMENT 16. Attach the terminals of Volta's 
 pile to the A terminals of the galvanometer and let the 
 time, resistance and observation be the same as in the pre- 
 ceding experiments. Do the deflections vary ? Why? 
 
 The Velio's pile should be taken apart and the plates 
 cleaned and dried as soon as possible after using it to avoid 
 corrosion of the plates. 
 
 EXPERIMENT 17. Examine the Daniell's cell* on the 
 side- table. Test it as to its polarization in the same way as 
 you did the cells in the preceding experiments. (T. 181). 
 
 EXPERIMENT 18. Test Bunsen's cell* as you did the 
 Daniell's and examine the Grove's cell. (T. 182, 183). 
 
 EXPERIMENT 19. Determine the constancy of the 
 Leclanch6 cell, having it connected up for ten minutes. 
 Record the readings every half minute. Now allow the 
 cell to stand on open circuit for a minute and then close 
 the circuit only long enough to take the reading the instant 
 the needle stops oscillating. Continue this for ten minutes 
 keeping the circuit closed as short a time as possible. Do 
 the results indicate a recovery in the strength of current? 
 If so, to what is it due? (T. 184). Because of the time 
 required for the needle to come to rest it will be quite as 
 instructive to compare the first swings of the needle in the 
 later part of this experiment. 
 
 It is found that the current from the voltaic cell rap- 
 idly diminishes in intensity, so that in a short time the ac- 
 tivity of the cell is very much reduced or may cease alto- 
 gether. This may be due to several causes, the chief of 
 which is the collection of hydrogen on the copper plate, 
 thus causing the polarization of the cell. 
 
 From Ohm's law (see page 2 2), it is apparent that any- 
 
 * Note, Specimens of these cells will be found on the side table. 
 
12 LABORATORY MANUAL 
 
 thing which tends either to diminish the E. M. F. or to 
 increase the resistance of a cell must cause a diminution 
 of the current strength. The chief effects of polarization 
 are the following, 
 
 1. The presence of hydrogen bubbles on the copper 
 plate sets up an E. M. F. in an opposite direction to the 
 E. M. F. acting from the zinc to the copper plate. The 
 effective E. M. F. is then equal to the difference between 
 the two. 
 
 2. The effective surface of the copper plate is de- 
 creased by the highly resistant hydrogen gas, and then the 
 internal resistance of the cell is increased and the current 
 is correspondingly decreased. 
 
 Methods of Preventing Polarization. i. Any 
 mechanical method of removing the hydrogen from the 
 negative plate such as brushing the plate or keeping the 
 liquid of the cell agitated would diminish polarization. 
 This method has never proved to be very satisfactory and 
 is now obsolete. 
 
 2. Polarization may be prevented by surrounding 
 the negative plate of the cell by some oxidizing material 
 which is capable of forming a chemical combination with 
 the nascent hydrogen. In this manner the two chief 
 causes of polarization are prevented. Nitric acid (HNO 3 ), 
 chromic acid (CrO 3 ), manganese dioxide (Mn O 2 ) and Cal- 
 cium hypochlorite (Ca (C1O) ) are commonly employed. 
 
 3. By placing the negative plate in some salt whose 
 metallic element can easily be replaced by nascent hydro- 
 gen, polarization can be entirely prevented. The chem- 
 istry of the Daniell and Chloride of Silver cells will 
 illustrate this principle. 
 
THE ELECTRIC BATTERY. 
 
 An electric battery is composed of one or more cells, 
 each cell consisting of any two dissimilar metals placed in 
 a liquid capable of chemically attacking either of them. 
 Any combination of such simple cells or elements is called 
 a battery. A battery composed of cells is still one of the 
 principal sources of electricity as it is used by Physicians. 
 One of the simplest forms of cells for such a battery con- 
 sists of a zinc and a copper plate with a dilute solution of 
 sulphuric acid for exciting liquid and is known as the 
 simple voltaic cell. 
 
 The generating plate is the name given the zinc or 
 other metal attacked by the liquid because part at least of 
 the chemical energy expended is utilized in the generation 
 of an electric current. This is also known as the positive 
 (-]-) plate and it invariably diminishes in size and weight 
 during the action of the cell. 
 
 The collecting plate is the term applied to the cop- 
 per, carbon, platinum or other metal used with the zinc. 
 This is also called the negative ( ) plate and it should 
 not be acted upon by the liquid in which it is immersed. 
 
 The elements consist of one generating and one col- 
 lecting plate. It is essential that the exciting liquid should 
 have a greater chemical affinity for the former than for 
 the latter. 
 
 The poles are the copper strip, from which the cur- 
 rent starts in the external circuit, and the zinc strip toward 
 which the current flows. These are known as the positive 
 (+) and negative ( ) poles or terminals respectively. 
 
14 LABORATORY MANUAL 
 
 The circuit constitutes the entire path of the cur- 
 rent. It consists of an internal part made up of plates 
 and liquid of the cell and an external part composed of 
 the connecting wires and any intervening body with which 
 they may be in contact. 
 
 A cell is on short circuit when its terminals are con- 
 nected by a short wire of no appreciable resistance. 
 
 A cell is on open circuit when its terminals are not 
 connected by a conductor or when the external resistance 
 is infinitely great. 
 
 THE CHEMICAL REACTION IN VARIOUS 
 BATTERIES. 
 
 The Simple Voltaic Cell. This cell is composed 
 of a strip of zinc and one of copper immersed in a 
 dilute solution of sulphuric acid (1:20 by vol.). During 
 the action of the cell the zinc is attacked by the acid, but 
 the hydrogen gas thus liberated is transferred by a series 
 of molecular interchanges to the copper strip where it 
 can first be seen. 
 
 If we represent the arrangement of the metals in the 
 liquid as follows: 
 
 Zn x _ z | ZnS0 4 | H,SO 4 H 2 | Cu. 
 
 The arrow represents the direction of the current 
 through the cell. The zinc and the hydrogen are dis- 
 placed in the cUrection of the current, while the sulphion 
 
OF ELECTROTHERAPEUTICS. 15 
 
 or SO 4 part of the acid, is displaced in the other direction. 
 All metals and hydrogen are electro positive, and travel in 
 an electrolyte with the positive current. Zinc sulphate is 
 formed at the expense of zinc and sulphuric acid, and 
 hydrogen is set free at the copper plate. The simple 
 chemical action taking place is, the displacement of the 
 hydrogen of the acid by zinc, forming zinc sulphate 
 instead of hydrogen sulphate. 
 
 The electro-motive force (E.M.F.)of this cell is about 
 i volt and this is reduced to ^ volt upon polarization. 
 
 The Daniell Cell. This cell most commonly con- 
 sists of a glass vessel containing a clear solution of cop- 
 per sulphate, in which is placed a cylinder of sheet copper 
 which serves as the negative plate. 
 Within the copper cylinder is 
 placed a porous cup of unglazed 
 earthen ware, which contains the 
 zinc rod immersed in dilute sul- 
 phuric acid or preferably a dilute 
 solution (5^) of zinc sulphate. 
 
 The Gravity Cell. Is a 
 modified form of the Daniell, in 
 which the two liquids are separ- 
 ated only by their difference in 
 density. 
 
 If we represent the arrange- 
 ment of metal plates as follows: 
 
 Fig. 5. Gravity Cell. 
 
 Zn x | H 2 So, | H 2 SO 4 || Cu So 4 | Cu SO 4 | Cu : 
 
 then after the first interchange it becomes 
 
 Zn x _! | Zn SO, | H 3 SO 4 || H 8 SO 4 | Cu SO, | Cu y+1 
 
1 6 LABORATORY MANUAL 
 
 It will be seen that all metallic elements and hydrogen 
 have been displaced in the direction of the current. The 
 zinc has lost one atom while the copper has gained one. 
 One molecule of zinc sulphate has been formed and one 
 of copper sulphate has disappeared. The hydrogen dis- 
 places the copper in Cu SO 4 and never reaches the copper 
 plate. Polarization is entirely prevented and the cell is 
 
 one of the most constant known. The E. M. F. is 1.08 
 volts. 
 
 The Bu-nsen Cell. This, like the Daniell, is a two 
 fluid cell. The zinc plate bent in the form of a cylinder, 
 is generally immersed in dilute sulphuric acid contained in 
 a glass vessel. A cup of unglazed earthenware is placed 
 within the zinc cylinder and contains a bar of carbon im- 
 mersed in strong nitric acid. The hydrogen formed at the 
 zinc plate traverses the porous cup, but then decomposes 
 the nitric acid with the formation of a corresponding 
 amount of water. The electric chain may be represented 
 as follows: 
 
 Zn x H 2 SO, | H 2 SO 4 || 2H NO 3 HNO 3 | C 
 
 After the first step in the chemical reaction this 
 becomes 
 
 Zn x _i | Zn SO 4 | H 2 SO 4 || 2 HNO 3 HNO 2 | H 2 O C 
 
 It will be seen that the nitric acid has been reduced 
 to nitrous acid (HNO 2 ), which in turn may lose an atom 
 of oxygen, becoming hypo-nitrous acid (HNO). Or further, 
 the nitric acid may be broken up completely, according to 
 the following reaction: 
 
OF ELECTROTHERAPEUTICS. 
 
 The nitric oxide gas (NO) thus formed on escaping 
 from the liquid immediately combines with oxygen of the 
 air, forming the red and very corrosive fumes of nitrogen 
 peroxide (NO 2 ). This cell is capable of furnishing a very 
 strong current, but the generation of corrosive fumes and 
 the fact that it requires attention at frequent intervals 
 cause it to be much less used than other forms of cells. 
 The E. M. F. is 1.8 volts. 
 
 The Bichromate Cell. The elements in this cell 
 are zinc and carbon plates immersed 
 in a fluid composed of bichromate of 
 potassium, (or chromic acid), sulphuric 
 acid and water. 
 
 When a solution of potassium bichro- 
 mate is treated with sulphuric acid, a 
 purely chemical reaction takes place, 
 resulting in the formation of chromic 
 acid. Thus: 
 
 K 2 Cr 2 7 +H 2 S0 4 = 
 
 K 2 S0 4 +H 2 0+2 Cr 8 . 
 
 Fig.6. Bichromate cell. The chromic acid, Cr O 3 , is the use- 
 ful agent to effect depolarization by the oxidation of hydro- 
 gen. The process is supposed to be represented in the 
 following reaction: 
 
 ,6 H+ 2 Cr 3 + 3 H 2 S0 4 =6 H 2 O+Cr 2 (SO,) 3 . 
 
 The final result is, therefore, the production of the 
 sulphate of zinc (at the positive plate), the sulphates of po- 
 tassium and chromium, and water. 
 
 The cell should be so constructed that both the zinc 
 and carbon plates can be removed from the liquid when 
 
 not in use. The E. M. F. is two volts. 
 ? 
 
l8 LABORATORY MANUAL 
 
 Battery Fluid. The following formulae are gener- 
 ally employed in the preparation of the battery fluid: 
 
 No. i. Sulphuric acid (commercial) 3 fluid oz. 
 
 Potassium bichromate (powdered) 2 oz. 
 
 Water 16 fluid oz. 
 
 *(Bisulphate of mercury 2 drachms. 
 
 First dissolve the bisulphate of mercury and then the potassium 
 bichromate in the water, and then slowly add the sulphuric acid with 
 constant stirring. Allow the liquid to cool before using. 
 
 No. 2. Chromic acid (Cr O 3 ) 2 oz. 
 
 Water 16 fluid oz. 
 
 Sulphuric acid [^ " " 
 
 (Bisulphate of mercury 2 drachms.) 
 
 This fluid is much to be preferred to the former, since the 
 absence of potassium salts prevents the formation of chrome alum, 
 K 2 Cr 2 (SO 4 ) 4 , which is very difficult of removal from the bottom of the 
 battery jar. 
 
 Fig. 7. A Series of Bichromate Cells. 
 
 The Leclanche' Cell. This form of cell is prob- 
 ably more used by physicians than all other forms taken 
 
 *NOTE. The bisulphate of mercury must never be placed in the 
 battery fluid, except when carbon is used as the negative plate. 
 
OF ELECTROTHERAPEUTICS. 
 
 collectively. The little attention required, the ease with 
 
 which it can be 
 
 restored and the 
 
 cheapness are all 
 
 factors which have 
 
 brought it into such 
 
 general use. The 
 
 elements are zinc 
 
 and carbon and the 
 | exciting liquid is a 
 
 strong solution of 
 
 ammonium chlor- 
 
 Pig. 8. Leianchs Cell. i d e. Depolarizers 
 are sometimes employed. When manganese dioxide 
 (MnO ) is used as a depolarizer it is packed about the 
 carbon plate and the arrangement may be represented as 
 follows: 
 
 Fig 9 Carbon 
 depo1 
 
 Zn 
 
 2 MnO 2 | C. 
 
 which becomes 
 
 Zn x _ z | Zn C1 2 | 2NH 4 C1 || 2 NH. 
 
 Mn 2 3 
 
 HO I C. 
 
 As a result of evaporation the double chloride of zinc 
 and ammonium is liable to crystallize on the zinc and on 
 the bottom of the glass jar. This should be prevented 
 as far as possible since it produces a deleterious eifect. 
 Owing to oxidation and local action the zinc rod is often 
 entirely severed at the surface of the liquid. This is one of 
 the first signs of disorder in the cell and can be almost indef- 
 initely postponed by protecting the zinc where it passes 
 through the surface of the liquid by a thin coat of pararHne. 
 This cell is well adapted to open circuit work. Its E. M, 
 
2O LABORATORY MANUAL 
 
 F. varies from 1.4 to 1.7 volts, but in a short time polar- 
 ization may reduce it to .7 volt from which it slowly 
 recovers. The tops of the battery jar and the carbon 
 plate are placed in melted paraffine and if on 
 setting up the cell, these parts are not moist- 
 ened by the battery fluid, disagreeable "creep- 
 ing " of the salts will be prevented. 
 
 The Chloride of Silver Cell. The ele- 
 ments in this cell are zinc and silver and on 
 the latter is fused the silver chloride which is 
 readily reduced by nascent hydrogen and thus 
 Fig. 10. serves as a depolarizer. The exciting liquid 
 may be ammonium chloride and in this case the chemical 
 reaction may be represented as follows: 
 
 Zn x | 2 NH 4 C1 | 2 NH 4 C1 | 2 AgCl | Ag y . 
 After the first interchange this becomes 
 
 Zn x _, | ZnCl 2 | 2 NH 4 C1 | 2 NH 4 C1 |-Ag y+a . 
 
 Polarization is prevented in a manner analagous to 
 that in the Daniell cell. Because of its small size this 
 cell adapts itself admirably to the construction of port- 
 able batteries for physicians use. It should never be used 
 to send anything but small currents as the materials would 
 otherwise quickly become exhausted. The E. M. F. is 
 about 1. 1 volts. 
 
 NOTES ON THE ACTION OF BATTERIES. 
 
 1. In all cells in which acid is used as the exciting 
 liquid the zinc must be amalgamated. In other types of 
 cells amalgamation of the zinc is not accompanied by any 
 deleterious effects. 
 
 2. During the action of a cell no effervescence of 
 gas should occur at the zinc plate, Such phenomena 
 
OF ELECTROTHERAPEUTICS. 21 
 
 indicate that the zinc should be more thoroughly amal- 
 gamated. 
 
 3. In batteries employing porous cups the fluid about 
 the mcorrodable plate should never be higher (nor in fact 
 quite as high) as the fluid about the zincs. This will 
 diminish one form of local action by delaying the diifu- 
 sion of the oxidizing fluid toward the zinc plates. 
 
 4. Most batteries should have their plates removed 
 from the liquid immediately after they have been used. 
 In two fluid cells the liquids should also be put in their 
 respective labeled bottles. 
 
 5. Detached carbon plates can be resoldered to their 
 attachments after a thin layer of copper has been depos- 
 ited upon one end by electrolysis. (This process will be 
 more fully treated under the subject of electrolysis). 
 
 METHODS OF AMALGAMATING ZINC. 
 
 Any expenditure of chemical energy within a cell 
 which does not contribute to the production of an electric 
 current is designated as local action. Such action may take 
 place either upon closed circuit or upon open circuit. 
 Such wasteful chemical actions are most often due to the 
 local electric circuits formed between commercial zinc 
 and its impurities. It is almost entirely prevented if the 
 surface of the zinc is covered by an alloy of mercury and 
 zinc, which is known as an amalgam. 
 
 The zinc plate may be amalgamated in the following 
 ways: 
 
 1. Clean the zinc in dilute acid and rub mercury 
 over its surface with a small cloth. The mercury spreads 
 readily if the zinc surface is properly cleaned. 
 
 2. An amalgamating fluid is prepared by dissolving 
 mercury in aqua regia (three parts of hydrochloric acid to 
 
22 LABORATORY MANtJAL 
 
 one of nitric acid) and then adding a small excess of 
 hydrochloric acid. If zinc be dipped into this solution 
 for a few moments its surfaces will receive a deposit of 
 metallic mercury. 
 
 3. A soluble salt of mercury is sometimes dissolved 
 in the battery fluid to keep the zinc amalgamated. 
 
 4. An alloy of zinc and mercury is sometimes pre- 
 pared for the positive plate. Such plates seldom need be 
 removed for amalgamating, but since they are much more 
 brittle greater care must be exercised in handling them. 
 
 NOTE. All forms of jewelry, such as rings, chains, etc., are liable 
 to injury by amalgamation and should consequently be removed before 
 working with mercury. 
 
 OHM'S LAW AND THE ELECTRIC UNITS. 
 
 In order to understand this most important law of 
 voltaic electricity it is first necessary to sharply distinguish 
 between the three following electrical quantities: 
 
 1. The Current (C) is the quantity of electricity 
 which flows past any point in a circuit in one second. 
 The unit of current strength is called the Ampere. 
 
 2. Electro-motive force (E. M. F.) or (E) may 
 be denned as that which causes electricity to move from 
 one point to another. It is sometimes spoken of as elec- 
 tric pressure. The unit of eletro-motive force is called 
 the Volt. 
 
 3. Resistance (R) refers to that which impedes or 
 checks the flow of electricity over a conductor. It is the 
 inverse of conductance. The unit of resistance is called 
 the Ohm. 
 
 Ohm's law may be expressed as follows: The current 
 which flows in a circuit varies directly as the electro -motive 
 force, and inversely as the resistance. 
 
OF ELECTROTHERAPEUTICS. 23 
 
 This relation may be expressed as 
 
 E 
 = R 
 
 when C, E and R represent respectively the units of cur- 
 rent, electro-motive force and resistance. From the above 
 
 p> 
 relation it is evident that E = CR and R = . 
 
 V-x 
 
 It follows that if any two of the three quantities be given 
 the third can be derived by calculation. 
 
 [The following are among the units adopted by the 
 Electrical Congress held in Chicago in 1*893. They are 
 designated International Units to distinguish them from 
 definitions previously adopted. 
 
 The International Ohm is represented by the resis- 
 tance oifered to an unvarying electric current by a column 
 of pure mercury at the temperature of melting ice, 14.4521 
 grammes in mass, of a constant cross-sectional area and 
 of the length of 106.3 centimeters. 
 
 The International Ampere is represented by the un- 
 varying electric current which deposits silver from a solu- 
 tion of silver nitrate in water at the rate of .001118 
 grammes per second. The solution must be of a definite 
 strength, and the whole process must be according to cer- 
 tain specifications. 
 
 The International Volt is that electromotive force 
 which, acting through a resistance of one ohm, will pro- 
 duce a current of one ampere. It is represented suffi- 
 ciently well by TiHHy of the electromotive force of a Clark's 
 standard cell at 15 C.] 
 
u 
 
 METHODS OF JOINING CELLS. 
 
 A. In Series. In this method the cells are con- 
 -T?=*> f~*~\ r*~r^ r~"~\ r^~ nested so that the posi- 
 
 | | | | | | !_J tive pole of one joins the 
 Fig. 11. negative of the next and 
 
 so on throughout the entire number of cells. 
 
 B. In Multiple Arc. In this arrangement the cells 
 are so joined that the pos- 
 itive poles are all con_ 
 
 nected together to form 
 a common positive pole 
 
 Fig. 12. 
 
 on one side, the negative 
 
 poles being also joined together to form a common neg- 
 ative pole on the other side (T. 168). 
 
 C. In Combination. Partly in series and partly 
 in multiple arc. In this arrangement groups of cells con- 
 nected in series are there joined 
 in multiple arc as if each group 
 were a single cell. 
 
 The group in the diagram 
 would be spoken of as three in 
 series and three in multiple arc, 
 involving nine cells, while five 
 Fig. 13. in series and eight in multiple 
 
 arc would require forty cells, etc. 
 
 OHM'S LAW APPLIED TO CELLS IN SERIES. 
 
 inn/i 
 
 KTTLT 
 TJUTT 
 
 Ohm's law being expressed by c =-~- * s true 
 
 R 
 
 when R represents the sum of all the resistances in circuit 
 
OF ELECTROTHERAPEUTICS. 25 
 
 and when E represents the algebraic sum of all the elec- 
 tro-motive force. If E = the E. M. F. of a cell and r = 
 its internal resistance, then the current sent through a 
 given external resistance (R) will be represented by 
 
 C- E 
 
 ~ 
 
 If m represents any number of cells joined in series it 
 follows, since both E and r increase with m, that the cur- 
 
 rent will be represented by C = - ~ 
 
 m /*-{- -K 
 
 When the external resistance or (R) o or when it is so 
 
 small as to be negligible C = - = it is evident 
 
 mi -\- o r 
 
 that m cells furnish no stronger current than one alone. 
 When on the other hand R is a large quantity as com- 
 
 pared to m r, C = and the current is therefore m 
 times as great as that from one cell. 
 
 OHM'S LAW APPLIED TO CELLS IN MULTIPLE. 
 
 When r equals the resistance of a single cell and we 
 have n such cells joined in parallel, the total resistance 
 
 becomes . The E. M. F. of n cells in multiple is no 
 n 
 
 greater than for a single cell, Ohm's law therefore becomes 
 
 E E 
 
 C = 
 
 :-+* 
 
 It follows that when the external resistance or (R) 
 = o the current is n times as great as for a single cell, since 
 
 C = 
 
26 . LABORATORY MANUAL 
 
 When, however, R is a large quantity the formula is 
 approximately true or when written C = =- in which 
 case n cells furnish no stronger current than a single cell. 
 
 OHM'S LAW APPLIED TO A MIXED CIRCUIT. 
 (A combination of cells in series and multiple arc.) Fig. i%. 
 If m is the number of cells in series and n the number 
 in multiple arc then the whole number of cells m n. 
 From preceding articles it follows that the resistance of 
 m cells in series = m r and if in n such groups be joined 
 in multiple arc the entire internal resistance will become 
 
 -- Since the E. M. F. is only affected by the number 
 
 n 
 
 of cells in series, Ohm's law becomes: 
 
 E E 
 
 c = - 
 
 mr_ , R r R 
 n r m n m 
 
 From this formula the following rule can be mathe- 
 matically derived, viz. A given battery will send the 
 greatest current through an external resistance when it is 
 so connected that the internal and external resistance are 
 
 equal. Or when - = R. 
 
CONSTRUCTION OF EXPERIMENTAL BATTERY. 
 
 An eight cell battery is now to be constructed from 
 the materials furnished. The wooden frame for holding 
 the battery jars and plates is furnished and should be fitted 
 up with the plates, wires, binding-posts, a device for rais- 
 ing and lowering the plates, etc. Contact is made with the 
 zinc plates by soldering bare copper wires 8 c.m. in length 
 to them. Similar wires are to be soldered to eight pieces 
 of sheet copper i by 1.5 c.m. 
 which can be wedged in con- 
 tact with thecarbon plates thus 
 making the contact with them. 
 For a more permanent form of 
 battery it would be advisable 
 to deposit first a thin layer of 
 copper upon one end of each 
 of the carbon plates by elec- 
 trolysis and then solder di- 
 rectly to the carbon plate. In 
 
 order that the battery when joined in series may yield the 
 required E. M. F., (16 volts), all contacts must be clean and 
 tight, and all local action prevented by thorough amal- 
 gamation of the zinc plates. 
 
 EXPERIMENTS WITH THE BATTERY. 
 
 EXPERIMENT 20. The galvanometer may be used to 
 determine the polarity of wires coming from a battery or 
 other generator of an elrctric current, thus indicating the 
 direction of the current (T. 197). Connect the terminals 
 of the Volta cell to the B terminals the long coil of the 
 
 Fig. 14. Experimental Battery. 
 
2 8 LABORATORY MANUAL 
 
 galvanometer and notice the direction in which the needle 
 is deflected. Now reverse the poles and observe that the 
 deflection is in the opposite direction. After having once 
 determined the deflection for a current of known direc- 
 tion, you can easily determine the polarity or direction of 
 current in a wire when the generator is not visible. The 
 importance of chis matter cannot be well over-estimated, 
 since in practice it is absolutely essential to know the 
 direction of current when passed through the body. 
 
 EXPERIMENT 21. Let the student opposite you ar- 
 range wires coming from a hidden cell that you may test the 
 polarity with the galvanometer. Determine the polarity 
 of the terminals marked X and Y, over the side-table which 
 are in connection with a cell in the dispensing room. Note 
 accurately the time when the test was made. 
 
 EXPERIMENT 22. Pass the current from a cell by 
 means of an insulated wiie, directly over and parallel to 
 the galvanometer needle. The wire can be wound around 
 the A terminals to hold it in position. Now bend the wire 
 leading from the cell to the galvanometer so that it also 
 lies nearly parallel to the needles. Why does this affect 
 the deflection ? Bring a magnet or a piece of iron near 
 the needle while the current is flowing and notice that the 
 deflection is changed. 
 
 EXPERIMENT 23. The E. M. F. of a cell is independ- 
 ent of the size of the cell. Prove by placing, in circuit 
 with your galvanometer, a resistance of 200 ohms, using 
 the A terminals or a still larger resist- 
 ~+~ ance with the B terminals. The latter 
 would be the better method in com- 
 paring the electro-motive forces of different cells. Prepare 
 a little cell (Fig. 15) by hollowing out a piece of carbon 
 so it will hold a drop of bichromate fluid, thus making 
 
OF ELECTROTHERAPEUTICS. 2Q 
 
 the carbon serve the double purpose of negative element 
 and battery jar. The positive element should be a small 
 pointed piece of zinc, which is to be dipped into the drop 
 of liquid when the circuit is to be completed. Pass the cur- 
 rent successively from a large bichromate cell, one cell of 
 your experimental battery and the small cell just prepared, 
 through the galvanometer. Do you get the same deflection 
 in each of the these cases-? What do the results indicate ? 
 
 EXPERIMENT 24. With the galvanometer and resist- 
 ance as in the previous experiment, connect one cell of the 
 experimental battery with a large bichromate cell so that 
 the current from one shall oppose that of the other. 
 Finally join the large cell in opposition to the little cell of 
 EXP. 23. In both cases observe the needle and account 
 for the results. 
 
 EXPERIMENT 25. Without changing the galvanome- 
 ter or resistance, connect one of the bichromate with a 
 voltaic cell so that their currents shall tend to oppose. 
 Why does the galvanometer needle move in this case and 
 not in the other? What is the logical conclusion, and 
 what is the direction of the current in this experiment ? 
 
 EXPERIMENT 26. The E. M. F. is independent of the 
 depth of fluid in the cell. Prove by leaving in circuit your 
 galvanometer and a resistance of at least 200 ohms, take 
 the galvanometer reading and then gradually raise the 
 plates from the liquid. Observe that the deflection does 
 not change until the plates leave the liquid. Why do you 
 use a high resistance in this experiment ? 
 
 EXPERIMENT 27. The E. M. F. of a number of cells, 
 in series, is equal to the sum of the electro-motive forces of 
 the several cells. Prove by putting in circuit with your 
 galvanometer, A terminals, a resistance of 200 ohms and 
 then pass the current from first one cell then two, three, 
 
LABORATORY MANUAL 
 
 etc., till the entire eight of the experimental battery are in 
 circuit. Take the galvanometer reading as each cell is 
 introduced and tabulate results, writing the current strength 
 opposite each deflection. Can you explain the results ? 
 (T. 212, fig. 121 ). 
 
 EXPERIMENT 28. The E. M. F. of a number of cells 
 in multiple arc is the same as that of one cell. Prove this 
 by having the galvanometer and resistance as in the pre- 
 ceding experiment, placing first one cell in circuit then 
 adding the remaining cells one at a time in multiple arc. 
 Take the galvanometer reading at each addition and ob- 
 serve that the results throughout agree with the above 
 statement. Do you think it necessary to have so much 
 resistance in circuit ? 
 
 EXPERIMENT 29. The E. M. F. of a battery com- 
 posed of x cells in series and y cells in multiple arc the 
 number of cells being xy ) is equal to x 
 times the E. M. F. of one cell. Having 
 galvanometer and resistance arranged 
 as in the past experiments, prove by 
 joining the cells in groups, of two in 
 series then joining the groups, one at 
 a time, in multiple arc, each time tak- 
 ing the galvanometer reading. It will 
 not be found difficult to verify the 
 above statement by the arrangement of 
 the cells. 
 
 EXPERIMENT 30. When groups of 
 cells are coupled against each other the 
 available E. M. F. is the difference 
 Fig. 16. Water Rheostat, between the electro-motive forces of 
 the opposing groups. Having in circuit a resistance of 200 
 ohms and the galvanometer, A terminals, couple two cells 
 
OF ELECTROTHERAPEUTICS. 31 
 
 of the experimental battery in series, and take the read- 
 ing. Now replace the two cells by the entire eight of the 
 battery so joined that three of the cells shall oppose the 
 other five. Does the needle indicate the same E. M. F. 
 in both cases ? Other combinations may be made to prove 
 the statement. 
 
 EXPERIMENT 31. No current of electricity can flow 
 except in a closed circuit, and the current is of the same 
 strength at all points in the circuit. Prove this by connect- 
 ing the entire battery in series with four resistances vary- 
 ing from 10 to 600 ohms. Now introduce the galvanome- 
 ter in the circuit between any two cells or resistances or 
 between the battery and a resistance, and notice that the 
 needle indicates the same current in each case. 
 
 EXPERIMENT 32. Having one cell of the experi- 
 mental battery send the current through the galvanometer 
 and take the reading. Now introduce in succession the 
 following resistances 25, 60, TOO, 150, 200 and 600 ohms. 
 In the last case use the B terminals also. In each case 
 take the deflection and by reference to the calibration 
 table find the strength of current. Also calculate the cur- 
 rent in each case by Ohm's law, and compare results. The 
 r of a cell may be called 4 ohms. 
 What are the sources of error ? 
 
 EXPERIMENT 33. Use the A ter- 
 minals of the galvanometer to meas- 
 ure the current given by i, 2, 3, 4 
 cells suc-cessively, coupling the cells 
 in series. Why do' 4 cells give no 
 
 Fig. 17. Graphite Rhostat. 
 
 greater current than one ? Calculate 
 
 the strength of current in each case. The resistance of 
 the galvanometer coil connected with the A terminals is 
 about one-tenth of an ohm. 
 
32 LABORATORY MANUAL 
 
 EXPERIMENT 34. Repeat EXP. 33, using a resistance 
 of from 100 to 200 ohms. Why does the current increase 
 as the cells are added? Calculate the current by Ohm's 
 law as before. 
 
 EXPERIMENT 35. Again repeat EXP. 33, but this time 
 coupling the cells in multiple arc instead of in series. Why 
 do you get a greater current from four cells than from one 
 in this case ? Again express the strength of current by 
 Ohm's law. 
 
 EXPERIMENT 36. With the A terminal of the galvan- 
 ometer and a resistance of 200 ohms, measure in succes- 
 sion the current from i, 2, 3 and 4 cells in multiple arc. 
 Why do the four give no greater current than one? 
 
 To measure the internal resistance of a cell join 
 two cells of the experimental battery in opposition and then 
 send the current from a large bichromate cell through 
 them, having the galvanometer in circuit. Note carefully 
 the deflection of the galvanometer. Now remove the two 
 cells joined in opposition and introduce in their place a 
 known resistance such as will make the deflection exactly 
 equal to the former reading. The current being the same 
 in the two cases, it is evident that the resistance introduced 
 equals that of the two cells of the experimental battery. 
 This conclusion is only allowable in case the E. M. F. 
 
 throughout the experi- 
 ment is kept constant, 
 
 C // ~lL If "|L If ix ,J and care must be taken 
 
 that the E. M. F. of 
 Fig. is. the cell does not fall 
 
 because of polarization. It is advisable to repeat this ex- 
 periment, joining two other cells of the experimental bat- 
 tery in opposition and then average the results. 
 
 EXPERIAIENT 37. Having the experimental battery 
 
OF ELECTROTHERAPEUTICS. 33 
 
 joined in series, pass the current through a glass of dis- 
 tilled water, using the B terminals of the galvanometer. 
 Now add enough salt to the water to make a i per cent, 
 solution. Calculate the resistance of the water in both 
 cases, letting the wires be immersed one inch and keeping 
 them one inch apart. Two per cent, and other solutions 
 may also be measured. 
 
 EXPERIMENT 38. Using from four to eight cells of 
 the experimental battery, determine by calculation from 
 Ohm's law, the resistance of the various parts of the 
 body, being careful in regions about the head and neck that 
 the current is barely strong enough to give a good reading 
 on the galvanometer. The electrodes should be carefully 
 covered with absorbent cotton and moistened in a solution 
 of common salt or ammonium chloride. In no case should 
 the metallic portion of an electrode be bronght in eontact with 
 any part of the body except when local electrolytic effects are 
 desired. 
 
 Determine the resistance through the following: 
 
 1. From one hand to the other; 
 
 2. From the hand to the elbow; 
 
 3. From elbow to the back of the neck; 
 
 4. Laterally through the neck; 
 
 5. From back of the neck to the temple; 
 
 6. Through the temples; 
 
 7. Through the hand; 
 
 8. Through the muscular part of the forearm. 
 
 Determine the difference in effect when large elec- 
 trodes are used instead of small ones. (Difference in cur- 
 rent density. See pg. 38.) 
 
 EXPERIMENT 39. Measure the unknown resistance at 
 i, 2, 3, 4 and 5 on block A or B, C, D, E, F, etc., by 
 calculation from Ohm's law, using, when possible, only 
 
34 LABORATORY MANUAL 
 
 sufficient battery power to give a deflection not much ex- 
 ceeding 10. For large resistance the B terminals will give 
 the best results, but in this case the resistance of the gal- 
 vanometer must be considered in the calculation. 
 
 EXPERIMENT 40. Resistance may be measured by 
 substitution. In this method the resistance to be meas- 
 ured is placed in circuit and the galvanometer reading 
 taken. The unknown resistance is then removed from the 
 circuit and in its place a known resistance is substituted 
 which will give exactly the same deflection as did the un- 
 known. The two resistances are then equal 
 
 (1) in case you succeeded in getting exactly the same 
 deflection in both cases, and 
 
 (2) if the E. M. F. of the battery has not varied dur- 
 ing the experiment. 
 
 Measure the R of two blocks of "unknowns," and 
 report the results to the instructor in charge. 
 
 DIVIDED CIRCUITS (T. 409). 
 
 If the poles of a battery be connected by two or more 
 conducting paths, the current will divide, each path carry- 
 ing a definite portion of the whole current. The principal 
 laws relating to divided circuits and joint resistances are 
 the following: 
 
 1. The sum of the currents in the several branches 
 is equal to the main current. 
 
 2. Each branch will carry such a proportion of the 
 whole current as its conductivity bears to the conductivi- 
 ties of all the branches. The conductivity of any path is 
 the reciprocal of its resistance. If the resistance = R 
 
 the conductivity = 
 
 Jx 
 
OF ELECTROTHERAPEUTICS. 
 
 35 
 
 3. The total conductivity of a number of branches 
 of a divided circuit is equal to the sum of the conductiv- 
 ities of the several branhes. 
 
 4. The joint resistance of any number of branches 
 
 in divided circuit is less 
 than the resistance offered 
 by any branch taken se- 
 parately. 
 
 EXPERIMENT 41. Put 
 in circuit with your gal- 
 vanometer (A terminals) 
 a R of 200 ohms and use 
 four cells in series. Note 
 the deflection. Without 
 interrupting the current 
 join the battery terminals 
 with three feet of German silver wire, number 30 to 36, and 
 note the effect on the deflection. The wire is a " shunt" 
 and forms one branch of a divided circuit. Now replace 
 the German silver wire by a short piece of copper wire 
 and notice that the deflection decreases still more. Why? 
 EXPERIMENT 42. With the same terminals of the 
 galvanometer, but using only 
 one cell, connect the term- 
 inals by two wires which 
 have a R of 25 and 100 
 ohms respectively. Now, 
 introduce the galvanometer 
 first into one circuit and Fig. 20. 
 
 then the other and observe the deflections. From your 
 results what relation can you deduce between the cur- 
 rent strength and the resistances of the branches? Write 
 out the ratio between the two currents. 
 
36 LABORATORY MANUAL 
 
 EXPERIMENT 43. Using but one cell, put in circuit 
 your galvanometer and a R of 50 ohms. Take the read- 
 ing. Now, in the same part of the circuit and between the 
 galvanometer and battery, place a shunt having a R of 50 
 ohms. Take the reading and then introduce a second 
 shunt having a R of 100 ohms beside the first. Notice 
 as each resistance is introduced the needle indicates an 
 increase of current. Why? 
 
 Take the reading in milliamperes and then remove the 
 galvanometer from the position in the main circuit closing 
 
 the circuit where it was re- 
 moved. Place it in turn in 
 each branch of the divided 
 circuit, being careful to keep 
 the circuit closed in all the 
 . 21. branches. In each case, re- 
 
 gister the current in milliamperes. Determine whether 
 the sum of the currents in the shunts equals that in the 
 main wire. Make a complete diagram showing the posi- 
 tion of each part in every case. 
 
 EXPERIMENT 44. Use one of the boards arranged 
 with a divided circuit. Place the galvanometer in the 
 main circuit. 
 
 1. Determine by substitution each of the six resist- 
 ances. 
 
 2. From the values obtained in one, calculate the 
 joint resistance of the six. 
 
 3. Determine the joint resistance of the six by the 
 substitution method. 
 
 4. From data thus far at hand calculate what per 
 cent, of the whole current will flow in each branch. 
 
 5. Determine experimentally, using one or possibly 
 two cells, the whole current flowing in the six part shunt. 
 
OF ELECTROTHERAPEUTICS. 
 
 37 
 
 6. Determine experimentally the strength of current 
 in each branch and what per cent, of the whole current 
 it is. 
 
 Prepare a table showing how your calculated and 
 experimental results agree. 
 
 The Shunt Method of Controlling Currents. 
 When any E. M. F. acts through a circuit it is found that 
 there is a gradual fall of 
 potential from one part of 
 the circuit to another. In 
 fact it can be easily demon- 
 strated experimentally, that 
 the fall of potential between 
 any two points in the circuit 
 is proportional to the resist- 
 "ance between them. If we 
 let R = whole resistance of 
 
 Fig. 22. Diagram of Graphite Shunt 
 Rheostat. See pg. 35. 
 
 the circuit. R'= resistance 
 between any two points of 
 the circuit. PD = whole potential difference; then the 
 difference of potential P'D' over the resistance of R' will 
 be determined by the following proportion: 
 
 PD : P'D' :: R :R' 
 
 It is evident from this that by varying the value of R', 
 P'D' will be correspondingly changed. 
 
 This principle readily adapts itself to the regulation 
 of currents for therapeutic uses, especially the commercial 
 currents which cannot be well regulated by the use of re- 
 sistance alone. Several forms of current controllers and 
 rheostats employing this principle are on the market, and 
 their efficiency in permitting a gradual increase of current 
 through the patient and then of again gradually reducing 
 
38 LABORATORY MANUAL 
 
 it to zero before removing the electrodes is certainly such 
 as to recommend them to a more extended use. 
 
 It is, perhaps, necessary to say, that such instruments 
 may be used to control all forms of current electricty ap- 
 plied directly to the body, the resistance in this case being 
 
 Fig. 23. Shunt Controller for Dynamo uuncu to. 
 
 comparatively great. They are not so readily adapted to 
 control the stronger currents required by the cautery or 
 exploring lamp. 
 
 CURRENT DENSITY. 
 
 Current density may be denned as the quantity of 
 current per unit surface of the electrode. Thus a current 
 of i milliampere entering the body from an electrode 
 
OF ELECTROTHERAPEUTICS. 39 
 
 whose active surface is i square centimeter, may be tem- 
 porarily considered as the unit of current density in elec- 
 tro-therapeutics. Consequently, in the application of a 
 given current to the body, the density of the current varies 
 inversely with the active surface of the electrode employed. 
 Except in such cases when the destructive electrolytic ac- 
 tion of the current is desired it is necessary to cover a 
 metallic electrode with some moist conducting material 
 and so place it upon the skin that the current shall flow 
 uniformly through all parts of the electrode. 
 
 ELECTROLYSIS. 
 
 The process of separating a compound chemical sub- 
 stance into its constituents by pasing an electric current 
 through it is called electrolysis. The substance thus 
 decomposed is called an electrolyte. The electrolyte is 
 always decomposed into at least two simple products 
 called "ions." The plate or surface at which the cur- 
 rent enters the electrolyte is called the anode, that by 
 which the current leaves being called the cathode. The 
 "ions" collecting at the anode are anions, while those at 
 the cathode are cathions. 
 
 The quantity of the electrolyte decomposed is directly 
 proportioned to the quantity of electricity passed through 
 it that is, to the current multiplied by the time and the 
 decomposition takes place at the same rate at all parts of 
 the circuit. A direct current is accurately measured by 
 determining experimentally the rate at which it effects elec- 
 trolysis. Thus the ampere is that current which will 
 deposit on the cathode ,001118 grams of silver per second 
 from a solution of a silver salt. The same current will 
 
4O LABORATORY MANUAL 
 
 decompose a grain of water in twelve minutes or will 
 deposit A of a grain of copper from CuSO 4 per minute. 
 
 An ion instead of remaining free may combine either 
 with the electrode or with the electrolyte, forming a sec- 
 ondary product. In general, in the electrolysis of the 
 salts of the alkali-metals, caustic alkali and hydrogen 
 appear at the cathode while free acid and oxygen appear 
 at the anode. Salts of the heavy metals usually give a 
 deposit of that metal at the cathode and a free acid and 
 oxygen at the anode. (T. 235). 
 
 In performing the following experiments perfect clean- 
 liness is necessary as slight traces of acid on the fingers or 
 table may interfere with the results of the experiment. 
 
 EXPERIMENT 45. Attach platinum electrodes to the 
 poles of the experimental battery and have the galvanom- 
 eter, B terminals, in circuit. Immerse the platinum of the 
 electrodes in a glass of distilled water. Observe the 
 strength of current and see whether you can observe any 
 traces of decomposition of the water. Now, add a few 
 drops of strong H 2 SO 4 and notice the changes that take 
 place in the fluid. 
 
 In this and the following experiments where chemical 
 changes are involved write formula showing the nature of 
 the changes. 
 
 BHHMMBSer 
 
 Fig. 24. Uterine Electrodes for Electrolysis. 
 
 EXPERIMENT 46. Electrolize a solution of CuSO 4 
 first using platinum and then copper electrodes. Employ 
 two cells of your battery and measure the current in each 
 
OF ELECTROTHERAPEUTICS. 41 
 
 case. The electrodes should be of the same size and 
 should be kept at the same distance apart throughout the 
 experiment. How do you account for the variation of 
 the current in the two cases? Try the experiment with 
 only one cell. (T. 487). 
 
 EXPERIMENT 47. Electrolize a solution of CuSO 4 
 using platinum electrodes. Notice the deposit of copper 
 on the cathode. This illustrates electro-plating, other 
 metals being deposited from solutions of their salts in a 
 similar manner. Hydrogen and the metals travel with the 
 current and are found on the cathode while oxygen and 
 the non-metals always collect at the anode. Determine 
 by this method the polarity of the terminals x and y on 
 the side-table. 
 
 EXPERIMENT 48. You can prove that the copper of 
 the anode is dissolved by using the copper covered plati- 
 num as anode in the electrolysis. In a short time the 
 copper will have disappeared. Tarnished copper will 
 become bright by being worn away at the anode while the 
 cathode increases in weight from the depositing of copper 
 upon it. Dissolve the copper deposit on the platinum by 
 dipping the latter in strong HNO 3 found on the side-table. 
 
 EXPERIMENT 49. Electrolize a solution of sodium 
 sulphate (Na 2 SO 4 ) using platinum electrodes. What gases 
 are liberated ? Is there a decomposition of the salt? Are 
 the gases primary or secondary products of decomposi- 
 tion? Make yourself familiar with the various chemical 
 changes taking place and write the chemical equations. 
 
 EXPERIMENT 50. Place some neutral Na 2 SO 4 solution 
 colored with litmus in a V tube and pass the current 
 through the electrolyte a few minutes, using platinum elec- 
 trodes. Notice the evolution of gases as before, also 
 that the solution becomes blue about the cathode and red 
 
42 LABORATORY MANUAL 
 
 about the anode indicating the formation of free acid and 
 free alkali. 
 
 EXPERIMENT 51. Having your hands clean and of 
 perfectly neutral reaction, lay a piece of blue litmus paper 
 on the palm and a red piece on the back of the hand. 
 Wet both pieces with a neutral solution of Na 2 SO 4 , press 
 clean copper electrodes against them and allow the current 
 to flow from the palm to the back of the hand. Use 8 
 cells of your battery and allow the current, which is quite 
 weak, to flow for about 10 minutes. Notice that the 
 papers have changed color. 
 
 EXPERIMENT 52. Repeat EXP. 51, but this time care- 
 fully cover the electrodes with absorbent cotton moistened 
 with the neutral Na 2 SO 4 solution. If the experiment is 
 properly performed the litmus paper on the hand will not 
 change color, but a piece in contact with the metal of the 
 electrodes will change color. The strength of current 
 being weak you should allow it to flow long enough to give 
 marked results. 
 
 This experiment shows the value of covered elec- 
 trodes and suggests the rule: 
 
 When using the galvanic or direct current, never place 
 bare or non-porous electrodes in contact with the skin or 
 mucous membranes unless you wish to obtain at the points of 
 contact the effect of free acid or free alkali. 
 
 EXPERIMENT 53. Electrolize a solution of NaCl, 
 using carbon electrodes. Notice the odor of free chlorine. 
 Now, use iron electrodes and notice that less chlorine is 
 given off, but that the anode is being corroded, giving a 
 light colored solution of iron salt near the anode. Finally 
 the alkali liberated at the cathode will pass over by dif- 
 fusion and cause a precipitate of ferrous and ferric 
 hydrates. Iron salts cause more or less discoloration of 
 
OF ELECTROTHERAPEUTICS. 
 
 43 
 
 the tissues in which they are set free. For this reason in 
 minor surgical operations such as the removal of superflu- 
 ous hairs, moles, warts, etc., especially on the exposed 
 
 parts of the body, the 
 cathode rather than the 
 anode should be em- 
 ployed. 
 
 EXPERIMENT 54. 
 Electrolize a solution 
 of Na 2 SO 4 using pla- 
 tinum electrodes and 
 a simple voltaic cell. 
 Place the galvano- 
 meter, B terminals, in 
 j^^H^^-^^j^^^ circuit and have the 
 
 Fig. 25. Chloride of Silver Battery. electrodes in position 
 
 before closing the circuit by placing the battery plates in 
 the liquid. Upon closing the circuit observe the galvano- 
 meter needle and explain why it returns to zero so quickly. 
 (T. 487). Now use one of your bichromate cells in a 
 similar manner and explain the difference in behavior. 
 
 EXPERIMENT 55. Polarized electrodes constitute an 
 independent source of E. M. F., which acts in an oppo- 
 site direction to that of the electrolizing current. This 
 can be shown in the following manner. Place in circuit 
 with your galvanometer the entire experiment battery 
 coupled in series and a pair of clean copper electrodes 
 between which is a layer of absorbent cotton wet with a 
 neutral solution of Na^C^. Allow the current to flow a 
 few minutes, observe the deflection and then break the 
 circuit by raising the battery plates. Wait till the needle 
 comes to rest and then connect the wires attached to the 
 battery terminals, thus making a circuit including only 
 
44 LABORATORY MANUAL 
 
 the electrodes and galvanometer. Notice the amount and 
 direction of the deflection. 
 
 EXPERIMENT 56. Remove a few hairs from the back 
 of your hand by electrolysis, using a fine sewing needle 
 as the electrode. The anode, which should be of medium 
 size and covered with absorbent cotton soaked with a 
 saline solution, may be placed upon any convenient sur- 
 face, as on the muscular part of the forearm or the palm 
 of the hand. Introduce the needle along a hair into the 
 hair follicle, have the galvanometer, B terminals, and bat- 
 tery in circuit and then complete the circuit by placing 
 
 Fig. 26. Needle Holder for Electrolysis. 
 
 the anode in position. The person operated on can be 
 taught to vary the strength of current both by pressure 
 upon the electrode and by varying the amount of surface 
 in contact with the anode. If properly done a little froth 
 will appear around the needle and the hair will come out 
 easily. Determine what was the greatest strength of cur- 
 rent during the operation. Try the effect of having all 
 parts in position and then suddenly turning on the current 
 by immersing the battery plates. Which do you consider 
 the better method? 
 
 In the actual electro-therapeutic practice, some form 
 of graduated rheostat or controller should be em- 
 ployed so as to permit the gradual entrance and with- 
 drawal of the current when the circuit is completed, with 
 the patient forming a part of it. By this means all unpleas- 
 ant shocks are avoided. 
 
 EXPERIMENT 57. It is often necessary in electrolytic 
 work that only a limited portion of the tissue should be 
 
OF ELECTROTHERAPEUTICS. 45 
 
 exposed to the action of the current or that the skin should 
 be protected from the caustic products at the point of 
 insertion of the electrodes. In such cases all but the tips 
 of the needles can be insulated by dipping them into alco- 
 holic shellac, protecting the tips by small pieces of cork. 
 Dry over a gas burner heating enough to drive off all 
 traces of alcohol and secure an even coating over the sur- 
 face. In removing a growth, requiring the insertion of both 
 electrodes, it will be found that the anode cannot be easily 
 withdrawn. If the current be reversed for a short time 
 the tissue about the electrode will soften and it can then 
 be removed without injury to the tissues. 
 
 EXPERIMENT 58. Electrolize a piece of fresh meat 
 which retains its juices, employing steel needles as elec- 
 trodes. Observe and describe the effect at the point of 
 
 Fig. 27. Dispert-ing Electrode. 
 
 insertion of both the anode and cathode needles. Insert- 
 ing each needle one inch and keeping them one inch 
 apart, determine the resistance in ohms of the fresh tissue 
 between them. 
 
 EXPERIMENT 59. Take 4 glasses out of your exper- 
 imental battery and wash them clean, then fill each half 
 full with a neutral Na 2 SO 4 solution containing a little alco- 
 holic solution of phenol-phthalein, and arrange them in a 
 row. Connect the remaining four cells of your battery in 
 series and connect the wires of this battery to the end 
 glasses containing the phenol-phthalein so that the wires 
 
4 6 
 
 LABORATORY MANUAL 
 
 dip into the fluid at the sides of the glasses. Complete 
 the circuit through the remaining glasses by short pieces 
 of copper wire, allowing the fluid in each glass to form as 
 wide an interval in the circuit as possible. Measure the 
 strength of current passing and also note the change of 
 color in the cells throughout the row after the current has 
 passed for a few minutes. Phenol-phthalein is a delicate 
 test for the presence of an alkali. Why should this elec- 
 trolytic change take place in the middle glasses with which 
 the terminal wires are not in contact? Is the amount of 
 chemical action the same in each of the four electrolytic 
 cells? 
 
 . 
 
 Fig. '28. Universal Connectors. 
 
 Laws of Resistance. In the solution of the prob- 
 lems here given, the following brief summary of the laws 
 of resistance should be borne in mind: 
 
 1. The resistance of conductors of the same mate- 
 rial and thickness varies directly as the length. 
 
 2. The resistance of conductors of a given material 
 and length varies inversely as the area of cross section. 
 Areas of circles are proportional to the square of their 
 diameters. 
 
 3. The resistance of a wire of a given length and 
 diameter depends upon the material of which it is made 
 that is, upon the specific resistance of the material. 
 
PROBLEMS. 
 
 The following problems are given with the view of 
 putting into practice the facts and principles that have 
 been treated of in the preceding experiments. To these 
 others will be added when needed for the purpose of illus- 
 trating or emphasizing certain rules or facts that may not 
 seem to be fully grasped by the student. 
 
 PROBLEM i. A certain battery whose r is .5 ohms 
 gives a current of i ampere through a R of 4 ohms. 
 What is its E. M. F. ? 
 
 PROBLEM 2. A battery of 40 cells each having an r 
 of .4 ohms is arranged 8 in series and 5 in multiple arc. 
 If the current flowing through a wire of no appreciable re- 
 sistance is 31.2 amperes, what must be the E. M. F. of each 
 cell ? What is the strength of current through each cell ? 
 
 PROBLEM 3. Twenty cells in multiple arc, each hav- 
 ing SL r of 30 ohms, send a current of J- ampere through 
 an external resistance of 1.5 ohms. What is the E. M. F. 
 of each cell ? 
 
 PROBLEM 4. Find the current flowing through a cir- 
 cuit composed of a galvanometer having a R of 100 ohms, 
 a battery which has an E. M. F. of 6 volts, and having a r 
 of .8 ohms, and connecting wires with a R of 5 ohms. 
 
 PROBLEM 5. The E. M. F. of a cell is r.8 volts and 
 its r .06 ohms. Would 5 of these cells in series light an 
 incandescent lamp which has a R of 10 ohms, and which 
 requires .8 amperes of current? How many milliamperes 
 of current are furnished ? 
 
 PROBLEM 6. Five cells, each having an E. M. F. of 
 
48 LABORATORY MANUAL 
 
 2.5 volts, and a r of .2 ohms are joined first in series and 
 then in multiple arc. Find the difference in the strength 
 of current if the R of the conducting wires is practically 
 zero. 
 
 PROBLEM 7. Find the current from 24 cells arranged 
 6 in series and 4 in multiple arc if the E. M. F. of each 
 cell is i volt and the r of each cell 3 ohms, the R being 45 
 ohms. 
 
 PROBLEM 8. Take 15 cells, each having an E. M. F. 
 of 1.5 volts and a. r of .2 ohms. What would be the cur- 
 rent strength if three of the cells were joined in opposition 
 to the other twelve ? 
 
 PROBLEM 9. A battery whose E. M. F. is 6 volts and 
 whose r is 2 ohms sends a current of 1400 milliamperes. 
 What must be the resistance offered in the circuit ? 
 
 PROBLEM 10. A battery of 5 cells in series, each cell 
 having an E. M. F. of 2 volts, produces 2 amperes of cur- 
 rent when the external resistance (R) is 3 ohms. What is 
 the r of each cell ? 
 
 PROBLEM n. The E. M. F. of a cell is i volt, its 
 internal resistance (r) 2 ohms. How many such cells 
 joined in series will be necessary to send a current of 55 
 milliamperes through an external resistance of 890 ohms? 
 
 PROBLEM 12. If the r of a cell is i ohm and you 
 have 90 such cells, how should they be connected so as to 
 send the strongest current through an external resistance 
 of 10 ohms ? 
 
 PROBLEM 13. If the E. M. F. of a cell is 2 volts, 
 and its internal resistance 4 ohms, what would be the least 
 number of such cells required to send a current of i am- 
 pere through an external circuit offering a resistance of 15 
 ohms? 
 
 PROBLEM 14. What is the best way to connect 12 
 
OF ELECTROTHERAPEUTICS. 49 
 
 cells, each having an E. M. F. of i volt and an internal 
 resistance of 3 ohms, in order to send the maximum cur- 
 rent through an external resistance of 30 ohms? 
 
 PROBLEM 15. If the R of 700 yards of copper wire 
 fs .91 ohms, what will be the R of 1320 yards? 
 
 PROBLEM 16. The R of a certain copper wire is 4.55 
 ohms. The R of a mile of this same wire is 1.3 ohms. 
 What is the length of the piece ? 
 
 PROBLEM 17. If the R of 130 yards of copper wire 
 re of an inch in diameter is i ohm, what is the resistance 
 of the same length of copper wire sV of an inch in diam- 
 eter ? 
 
 PROBLEM 18. What is the R of a mile of copper 
 wire which has a diameter of 65 mils, if the R of a cop- 
 per wire 80 mils in diameter is 8.29 ohms ? (A mil is unnr 
 of an inch). 
 
 PROBLEM 19. What length of copper wire 4 mm in 
 diameter would be equivalent in resistance to 12 yards of 
 copper wire i mm in diameter? 
 
 PROBLEM 20. Find the joint R of two wires offering 
 respectively 5 and 7 ohms resistance. 
 
 PROBLEM 21. The joint resistance of two wires is 
 3 ohms and one of them has a resistance of 9 ohms. What 
 is the resistance of the other ? 
 
 PROBLEM 22. What must be the resistance of the 
 shunt used with a galvanometer whose resistance is 4500 
 ohms so that the resistance of the shunted galvanometer 
 shall be 450 ohms? 
 
 PROBLEM 23. Find the joint resistance of three wires 
 offering respectively 5, n and 15 ohms. 
 
 PROBLEM 24. Three wires in a divided circuit have 
 resistance of 6, 7 and 15 ohms respectively. How would 
 a current of i ampere divide in this circuit ? 
 
 4 
 
50 LABORATORY MANUAL 
 
 PROBLEM 25. Three wires in divided circuit have a 
 joint resistance of 6 ohms. What resistance must be used 
 as a shunt to reduce the joint R to 3 ohms? 
 
 PROBLEM 26. A galvanometer whose resistance is 
 5000 ohms is shunted by a wire having a resistance of 506 
 ohms. If a current of 30 milliamperes is sent through 
 the circuit what will be the strength of current through 
 the galvanometer? 
 
 PROBLEM 27. If a current of 20 ma. is passed through 
 the body, the anode a circular disk of metal 3 centimeters 
 in diameter applied to the neck, the cathode 10 centi- 
 meters square placed on the abdomen, what would be the 
 density of current per centimeter of surface at the anode ? 
 What amount of electric energy (Watts i. e., C. X E. M. F.) 
 would be expended at the anode in 10 minutes of time, 
 provided the R at that point is one-fourth of the entire 
 resistance ? 
 
 PROBLEM 28. If the R, including a portion of the 
 body, is 3500 ohms and the skin contact with the elec- 
 trodes furnishes 3000 ohms of this resistance, how much 
 electric energy would be expended at the skin contact in 
 a treatment lasting 15 minutes when the voltage is 50 ? 
 What would be the result? How is that result to be 
 avoided? 
 
 PROBLEM 29. W T hen two electrodes each 3 centi- 
 meters square are used to conduct a current of 12.5 ma. at 
 a voltage of 70 through the spine, one electrode being 
 placed on the back of the neck and the other over the 
 sacrum, how much electric energy reaches the deep tissues 
 of the body if the skin contacts furnish two-thirds of the 
 entire resistance ? How could the amount of energy 
 expended on the deeper portions be increased without 
 changing the voltage ? 
 
PHORESIS, ANAPHORESIS, CATAPHORESIS. 
 
 It has long been known that the direct electric cur- 
 rent has a marked mechanical effect in carrying certain 
 liquids and solutions through porous partitions or mem- 
 branes so as to either accelerate or retard the ordinary 
 processes of osmosis. This effect, probably very closely 
 related to that of electrolysis, is generally such as to 
 convey the substances in solution in the liquid through 
 the dialyzing partition, or membrane in the direction of the 
 current, thus causing a decreased anodal and an increased 
 cathodal pressure, although in some instances the reverse of 
 this is true. These phenomena, which are most manifest 
 in badly conducting liquids, are generally 
 included under the term electric osmose 
 but when applied to living animal tissues 
 for therapeutic purposes are called cata- 
 phoresis or anaphoresis according to 
 the direction in which the substance is 
 conveyed. 
 
 The numerous experiments of De la 
 Rive established the following generaliza- 
 tions regarding electric endosmose: 
 
 ''The force with which a galvanic 
 current transports a liquid through a por- 
 ous partition from the positive to the 
 negative wall is measured by a pressure 
 which is directly proportional to the intensity of the 
 current, to the electric resistance of the liquid, to the 
 thickness of the porous partition, and inversely propor- 
 tional to the surface of that partition." 
 
 Pig. 29 Phoresiis 
 electrode. 
 
52 
 
 LABORATORY MANUAL 
 
 EXPERIMENT 60. The passage of substances into or 
 out of the tissues of the body may be hastened by electric 
 osmosis, that is by the anaphoric or cataphoric action of 
 the current. Thoroughly wash your hands with soap and 
 water, then place on the back of each 
 wrist a square cotton-covered electrode 
 which has been saturated in a solution of 
 methylene blue. Now pass the current 
 from your 8-cell battery through the body 
 from wrist to wrist. Measure carefully 
 the current and allow it to flow till the 
 equivalent of 5 ma. has passed for 10 
 minutes. Discontinue the current and 
 again wash the wrists and examine 
 whether there is any difference in the 
 discoloration of the skin which was 
 under tne anode and cathode. 
 
 EXPERIMENT 61. Repeat the last 
 experiment employing a cathode moistened with a solution 
 of common salt and a metallic or better a carbon anode 
 separated from the skin by two small squares of blotting 
 paper soaked in a 4 per cent, solution of cocaine hydro- 
 chloride. The current should be measured carefully and 
 permitted to pass for at least ten minutes. When it 
 is discontinued the part under the electrode should be 
 examined to see whether any local anaesthesia has been 
 produced. This can be tested by pricking the surface 
 with a needle. 
 
 Electric osmosis, either as anaphoresis or cataphor- 
 esis, is employed in electro-therapeutics for 
 
 i st. Conveying medicines in solution into the tissues 
 through the skin or mucous membrane surfaces. This 
 can be made local or general medication according as a 
 
 Fig. 30 Section of 
 Phoresi* Electrode. 
 
OF ELECTROTHERAPEUTICS. 53 
 
 limited area or the entire skin surface is subjected to the 
 action; 
 
 2nd. Removing injurious substances from the tissues, 
 abnormal accumulations of fluids in joints, dropsical 
 effusions, etc. 
 
 Cataphoresis is at present much used by the dentist 
 to obtund sensitive dentine. The anodal effect of the 
 current is of itself sedative but its anaesthetic action is 
 greatly increased when a substance, which is soothing to 
 sensory nerves and is capable of being conveyed into the 
 tissues by means of cataphoric action, is used in solution 
 on the anode. 
 
 PHYSIOLOGICAL ACTION OF DIRECT CURRENTS. 
 
 There are certain reactions which direct or galvanic 
 currents bring about when applied to living animal tissues 
 which cannot be regarded as physical or mechanical effects 
 of the current, since they are dependent upon the pecu- 
 liar properties of living animal tissues and the nature of 
 their response as such to this form of stimulant or excit- 
 ant. These it seems proper to designate as physiological 
 effects, and as they have long served as a rational basis 
 for therapeutic applications with this form of current a 
 special mention of them is required. The physiological 
 effects that are best known to us from experiments in the 
 physiological laboratory and from electro-therapeutic 
 observations may be classified as: 
 
 Reactions of muscular tissue; 
 
 Reactions of nerve tissue; 
 
 Reactions of protoplasm. 
 
 Both the striped and unstriped varieties of muscle 
 can be caused to contract by the application to them of 
 
54 LABORATORY MANUAL 
 
 either pole of a direct current, the other pole being placed 
 upon some distant point of the body to complete the 
 circuit. The strength of the response in normal muscle 
 will depend upon the strength and electro-motive force of 
 current used. This form of current causes a contraction 
 only at the moment when it is closed or opened; at the 
 "make" and "break" of the currents as they are called. 
 The reactions in unstriped muscle resemble, in general, 
 those of the striped variety except that unstriped muscle 
 responds more slowly to the stimulation. 
 
 The results following the application of the direct 
 current to nerve tissue differs according to the nature of 
 the tissue influenced /'. e., whether it is peripheral nerve, 
 sensory, motor, secretory or nerve cells in brain, cord, or 
 ganglia. Thus, applications along the course of a motor 
 nerve will cause contractions in the muscle supplied by 
 that nerve similar to those obtained by the direct applica- 
 tion to the muscle itself. 
 
 Sensory nerves respond to direct current applications 
 by increase or decrease of excitability, according as the 
 application is made with the anode or cathode. The 
 result of anodal application is to decrease the excitability 
 and the effect is called anelectrotonus. The result of 
 the cathodal application, on the other hand, is to increase 
 the excitability and this effect is called catelectrotonus. 
 
 EXPERIMENT 62. Join two experimental batteries in 
 series, put in circuit the galvanometer, B terminals, a 
 circuit breaker, pole changer and a high-resistance rheo- 
 stat. Use a large dispersing cotton-covered electrode and 
 a small active electrode which should be applied over the 
 median nerve above the elbow joint. By means of the 
 pole-changer the small electrode can be quickly changed 
 from anode to cathode and the current strength can be 
 
OF ELECTROTHERAPEUTICS. 55 
 
 readily changed by means of the rheostat. Carefully 
 determine the strength of current that will produce: 
 
 1. Cathode closing contraction (C. C. C. ). 
 
 2. Anode closing contraction (A. C. C. ). 
 
 3. Anode opening contraction (A. O. C.). 
 
 4. Cathode opening contraction (C. O. C. ). 
 
 This experiment may be done by four students work- 
 ing together. Make a sketch of the entire circuit. 
 
 EXPERIMENT 63. Apply two cotton-covered elec- 
 trodes about 1.5 inches square to corresponding parts of 
 the flexor surface of each forearm. Place a rheostat, gal- 
 vanometer and a i6-cell battery in circuit and allow a 
 current of 10 ma. to flow for at least 5 minutes. After 
 the electrodes have been removed apply the points of a 
 pair of compasses to the two surfaces and in each case 
 determine the distance between the points in millimeters 
 at which they can be distinguished by sensation alone. 
 Can you detect any difference in the sensibility of the 
 two surfaces? Also note any difference in the external 
 appearance of the two surfaces which were under the 
 influence of the current. 
 
 CATALYSIS. 
 
 The term catalysis was first employed by 'Remak to 
 include the various processes, partly demonstrable and 
 partly theoretical, which attended the application of a 
 direct current to diseased tissues and which often resulted 
 in a restoration of normal function. These processes are 
 both physical and physiological, some of them being of a 
 very complex nature. 
 
 It is believed that neither the electrolytic, cataphoric, 
 
56 LABORATORY MANUAL 
 
 anaphoric, contractile, nor electrotonic actions of the 
 direct current which have already been described are suffi- 
 cient to account for the permanent benefit which the 
 employment of such currents in therapeutics affords. It 
 is assumed therefore that there are a variety of effects not 
 yet experimentally demonstrable but still theoretically 
 quite probable, that follow from the passage of the cur- 
 rent in addition to these that can be readily observed, and 
 it is both these known and assumed actions that the word 
 catalysis is intended to cover. The result you obtained in 
 EXP. 59 will serve, in a measure, to illustrate this inter- 
 polar action of the direct current when passed through 
 the living organism. 
 
 THE GALVANO-CAUTERY. 
 
 The energy of an electric current may manifest itself 
 in a variety of ways, such as magnetic, mechanical, 
 chemical and radiant energy, the latter including various 
 phenomena among which the most common are heat and 
 light. In every case where a current is controlled by the 
 introduction of resistance into the circuit, without a 
 counter electro-motive force such as is furnished by an 
 electric motor or an electrolytic cell, the energy is used 
 up in the form of heat. In the vast majority of electrical 
 operations the heating effects of the currents are wasteful 
 and are, so far as possible, avoided or reduced to a mini- 
 mum. The electric cautery is one of the appliances in 
 which this property of the current can be utilized. The 
 amount of heat developed in a conductor is proportional 
 
 ist, to the resistance; 
 
 2nd, to the square of the strength of current; and 
 
 3d, to the time. 
 
OF ELECTROTHERAPEUTICS. 57 
 
 The temperature to which a body of a given resist- 
 ance will be raised by a given current depends upon the 
 nature of the resisting substance, /'. e. upon its specific 
 heat, and also upon the form of the conductor. The 
 temperature will continue to rise till the rate at which it is- 
 lost by conduction, convection and radiation is equal to 
 the rate of generation by the current. 
 
 From these general considerations it becomes evident 
 that all parts of the circuit in cautery work should have 
 the least possible resistance except the part which is to be 
 heated. For this reason cautery batteries are made of 
 large plates placed very close together and all the neces- 
 sary conducting wires are relatively large and of low 
 resistance (T. 426 429). 
 
 EXPERIMENT 64. To show the necessity of a strong 
 current in working with the cautery, connect the poles of 
 your battery, arranged two in series and four in multiple 
 arc, by ten inches of No. 36 copper wire. Observe to 
 what extent the wire is heated and then slowly shorten it 
 and notice whether the temperature rises. Repeat, this 
 time using german silver wire of the same length and 
 diameter. 
 
 EXPERIMENT 65. Show the necessity of having a 
 low internal resistance by using first one cell of the experi- 
 mental battery and then one of the large bichromate cells 
 on the side table, in. each case passing the current through 
 the german silver wire used in the last experiment. Is the 
 effective E. M. F. in the two cells the same after the cur- 
 rent has been flowing a few minutes ? Give your reasons. 
 
 EXPERIMENT 66. Twist together three pieces of 
 iron or german silver wire six inches in length and pass 
 the current of your battery joined in multiple arc through 
 it. Notice the rise in temperature. Now replace the 
 
58 LABORATORY MANUAL 
 
 twisted strand by a single wire two inches in length, and 
 see whether the temperature is higher than before. Is the 
 strength of current the same in the the two cases? How 
 do you explain the difference in the results? (T. 429). 
 
 Fig. 31. Primary Battery for Cantery Work. 
 
 
 
 The heat generated in the two cases should be exactly the 
 same but the mass of metal and surface exposed in the 
 two cases are very unequal. It should be apparent that 
 wires having a high specific resistance and which do not 
 easily corrode are best adapted for use in the cautery. 
 Platinum meets these requirements and has the additional 
 
OF ELECTROTHERAPEUTICS. 59 
 
 advantage of not being easily fused; even it, however, can 
 be melted by the electric current. 
 
 EXPERIMENT 67. Make a small cautery electrode 
 like the model shown you. Connect it to one of the 
 large bichromate cells. What causes the rapid falling in 
 temperature after the current has been flowing a few min- 
 utes ? Notice the effect of raising and lowering the plates 
 in the fluid. Examine the two forms of cautery batteries 
 and the methods of controlling the current in each. It is 
 evident that the plates should be left in the fluid only so 
 long as the cautery is in immediate use. Could you heat 
 a cautery with six Daniell cells? 
 
 EXPERIMENT 68. Use one of the cautery batteries 
 to heat the cautery electrode and when it is glowing, 
 immerse part of it in water and notice the effect on the 
 remaining part of the fine wire. What is your explana- 
 tion? A similar effect attends the use of the cautery in 
 practice and unless a ready means of regulating the cur- 
 rent is at hand, it may be melted (T. 404). 
 
 SOURCES OF CURRENT FOR THE ELECTRIC CAUTERY. 
 
 The strength of current required for heating electric 
 cauteries varies from i to 25 amperes. This current is 
 far in excess of that used in therapeutics when the current 
 traverses the body, and for this reason special forms of 
 generators and controllers are required for doing cautery 
 work. A suitable current may be obtained from: 
 
 1. Primary batteries. 
 
 2. Secondary or storage batteries. 
 
 3. The dynamo. 
 
 Primary Batteries. Since the external resistance 
 in a cautery circuit is very small (seldom exceeding. i 
 ohm) it is necessary that a cautery battery should be 
 
6o 
 
 LABORATORY MANUAL 
 
 specially constructed so that its internal resistance shall 
 be reduced to a minimum. The E. M. F. may vary from 
 2 to 6 volts. In order to deminish the internal resistance 
 of a battery, the plates should be large and near together 
 and every precaution should be taken to prevent polariza- 
 tion. If cells of large size are inconvenient and make 
 the battery too cumbersome, smaller cells may be em- 
 
 Fig. 32. 
 
 ployed provided they are joined in multiple arc. By 
 using a large bichromate cell with large plates of carbon 
 and zinc the resistance may be brought down to .15 ohms. 
 This cell acting through a cautery electrode of . i ohm 
 resistance would furnish 8 amperes of current. 
 
 E 
 
 C = 
 
 22 
 
 C = - - = 8 amperes. 
 
 o.i + 0.15 0.25 
 
 R -j- r 
 
 In all forms of primary batteries which generate large 
 currents, polarization soon tends to lessen the output of 
 current. This difficulty may be prevented by keeping the 
 
OF ELECTROTHERAPEUTICS. 6l 
 
 plates of the battery constantly in motion, thus bringing 
 fresh battery fluid in contact with the plates. By having 
 at the outstart a current capacity far in excess of the 
 amount required to heat the cautery, a suitable rheostat 
 in circuit to regulate the current to the required amount 
 would be the most convenient method of overcoming the 
 polarization effects. 
 
 Secondary or Storage Batteries. A well con- 
 structed and newly charged storage battery furnishes an 
 ideal source of current for cautery purposes. The current 
 should be controlled by a rheostat such as has already 
 been mentioned. The care of a storage battery and the 
 uncertainty of its charge at any time are drawbacks which 
 prevent its general use by physicians. 
 
 . Dynamo Circuits. The currents from both direct 
 and alternating current dynamos may be controlled by 
 heavy wire resistance for heating electric cauteries. This 
 is however a cumbersome aud expensive method. 
 
 When, however, these currents are changed by trans- 
 formers they become the most convenient sources of cur- 
 rent for electro-cauteries and exploring lamps, this being 
 especially true of the transformed alternating current. 
 
 Attention will be given to these methods of transfor- 
 mation of dynamo currents further on in this work. 
 
SOURCES OF CURRENT FOR ELECTRIC LIGHT. 
 
 The electric light possesses marked advantages over 
 all other means for illuminating the cavities of the body 
 In general, it may be stated 
 that the sources of current for 
 electric cauteries will also 
 serve to light the exploring 
 lamps used for diagnosis or illu- 
 mination. The conditions of the circuit are, 
 however, somewhat changed and these de- 
 mand corresponding changes in the source 
 of the current Thus, the resistance of the 
 filament of the small lamps varies from 6 to 
 30 ohms. The current strength required to 
 raise these lamps to incandescence is from 
 3 to 1.6 amperes. Thus a greater E. M-. F. 
 is necessary than for heating a cautery and 
 the internal resistance becomes a factor of 
 very aiuch less importance. A battery of 10 
 bichromate cells in series, when r = i ohm, 
 would send a current of i ampere through a 
 lamp of 10 ohms resistance. 
 
 2 X 10 
 
 C = 
 
 20 
 
 -, x : = -- = i ampere. 
 
 (i X 10) -f 10 20 
 
 Fig. 33 Tongue 
 depressor and 
 throat illu- 
 minator. 
 
 In lighting lamps to be used in diagnosis 
 it is necessary that the current be controlled either by a 
 rheostat or by some ready means for varying the E. M. F. 
 acting through the lamp. The transformed alternating 
 
OF ELECTROTHERAPEUTICS. 63 
 
 dynamo current is a most desirable and convenient source 
 to employ for this purpose. 
 
 THE STORAGE OR SECONDARY BATTERY. 
 
 As was seen in EXP. 55, a difference of potential 
 exists between two like plates immersed in a liquid, by 
 virtue of the products of electro-chemical decomposition 
 set free at their surfaces. Such cells are known as storage 
 cells or accumulators. The E. M. F. of the accumulator 
 depends upon the tendency for the liberated "ions "to 
 recombine and its magnitude is strictly proportional to 
 the energy with which this recombination tends to take 
 place. Thus, in the electrolysis of water, the elements O 
 and H by their recombination yield an E. M. F. of 1.47 
 volts and consequently no cell or other source of current 
 can effect the electrolysis of water unless it has an electro- 
 motive force of, at least, 1.47 volts. It should be borne 
 in mind that it is not electricity but chemical energy 
 which is stored up by the current and thac the latter under 
 proper conditions is again reconverted or transformed 
 into the energy of an electric current. In the progress of 
 development of the storage cell two main problems were 
 prerented, viz: 
 
 1. How to retain a large amount of the liberated 
 "ions" upon the two electrodes, 
 
 2. How to prevent the dissipation of the energy 
 while the cell is on open circuit. 
 
 Considerable advancement has been made in recent 
 years but the second problem has proved to be far the 
 more difficult to solve. 
 
64 LABORATORY MANUAL 
 
 Great care must be exercised in the handling of a 
 storage battery as an accidental " short circuit " is very 
 destructive to the plates. In charging the cell the direc- 
 tions of the manufacturer should be strictly^ observed and 
 where practicable it is best to entrust this task to the 
 manufacturer or to some local electrician. 
 
 A recent form of storage battery is one consisting 
 practically of two lead plates, the positive of which is 
 intimately covered with red lead (minium, P 3 O 4 ) and the 
 negative with litharge (P^O). The electrolyte is sul- 
 phuric acid, one part by weight to four of water. As 
 soon as the plates are immersed in the fluid the following 
 reaction takes place. The lead oxides are converted into 
 lead sulphate. 
 
 P 3 O 4 + 2H 2 SO 4 = P0 2 + 2 PSO 4 + 2H 2 O. 
 
 The changing current liberates hydrogen and oxygen. 
 The latter goes to the positive plate and changes the lead 
 sulphate to lead peroxide and sulphuric acid. 
 
 2 PSO 4 + 2H 2 O -f O 2 = 2PO 2 + 2 H 2 SO 4 . 
 
 Hydrogen goes to the negative plate and changes the 
 lead monoxide to spongy lead with the formation of water. 
 
 PO + H 2 = P + H 2 O. 
 
 It also acts upon the lead sulphate, changing it to 
 spongy lead and sulphuric acid. 
 
 2 P^SO 4 + 2H 2 = 2 P + 2 H 2 SO 4 . 
 
 The chemical reaction of the discharge is the forma- 
 tion of lead sulphate upon both plates. 
 
 EXPERIMENT 69. Construct a storage battery, using 
 lead plates with a paste made of lead oxide and sulphuric 
 acid (1:4), held in place by a layer of absorbent cotton. 
 
OF ELECTROTHERAPEUTICS. 65 
 
 Roll the plates tightly together, being careful to have 
 them completely covered with cotton, and then immerse 
 in the sulphuric acid solution. To get good results it 
 is advisable to first charge and then discharge the bat- 
 tery. First pass the charging current in one direction, 
 then reverse the current and finally pass it again in the 
 first direction. Connect the plate covered with lead to 
 the positive pole while charging. When your accumulator 
 is finally charged have its E. M. F. measured and then 
 proceed to determine its internal' resistance by Ohm's 
 law. From these results compute the current which the 
 cell would furnish when working on short circuit. 
 
 NOTE. Your experimental battery must be in good condition for 
 charging and it is well to join it 2 in multiple arc and 4 in series. The 
 time required for each charge and discharge should be at least 10 min- 
 utes. The galvanometer may be used to assure you that you have a 
 charging current and to detect any variations in the same. 
 
 THE ROTARY TRANSFORMER. 
 
 The rotary transformer shown in the accompanying 
 figure is a device for changing the ordinary direct dynamo 
 current of high voltage to a direct current of low voltage 
 such as is suitable for heating cautery wires and lighting 
 exploring lamps. The machine is virtually an electric 
 motor and dynamo combined, the current supplied to the 
 motor being of a higher E. M. F. than that furnished by 
 the dynamo. Except for a slight loss in transformation 
 the energy (C. V. = current X potential difference) sup- 
 plied to the machine and that yielded by it should be 
 equal. The old method of controlling dynamo currents 
 for cautery work by introducing heavy wire resistance in 
 
 5 
 
66 
 
 LABORATORY MANUAL 
 
 circuit is both very cumbersome and expensive since less 
 than 10 per cent, of the energy is usefully employed. 
 
 A similar waste of en- 
 ergy can be obviated by 
 charging storage batter- 
 ies with the transformed 
 current instead of em- 
 ploying the ordinary dy- 
 namo current controlled 
 by resistance. 
 
 A suitable rheostat 
 must be employed in 
 the cautery or light cir- 
 cuit for the purpose of 
 controlling the current 
 more accurately. 
 Fig. 34. Rotary Transformer. The rotary transform- 
 
 er is not only a conven 
 
 ient and economical means for securing a direct current 
 for therapeutic purposes but it is also a safe means. When 
 taking a supply of current for therapeutic purposes from 
 dynamo mains carrying a current of high voltage all danger 
 of subjecting a patient to an excess of current or voltage 
 is entirely removed by this device. 
 
MAGNETISM. 
 
 A close relationship exists between current electricity 
 and magnetic phenomena. Induced current electricity, 
 which plays a very important part in therapeutics, is the 
 result of magnetic action. There is also good reason to 
 believe, from the results of recent investigations, that 
 magnetism itself has some direct therapeutic value. At 
 least we have discovered from experiments conducted for 
 a number of months in this laboratory that the growth of 
 growing animals is accelerated when subjected for some 
 time to the influence of alternating magnetic fields. These 
 considerations render it advisable for us to review by 
 experiment the fundamental phenomena relating to the 
 relationship between electricity and magnetism. 
 
 In performing the following experiments certain facts 
 should be kept in mind: 
 
 1. Rough and careless handling of a permanent 
 magnet is very detrimental to its strength and may destroy 
 its usefulness; 
 
 2. The swinging needle of the galvanometer may 
 have its magnetic properties changed or destroyed by 
 bringing strong magnets too near it and thus the instru- 
 ment may be rendered quite useless. 
 
 EXPERIMENT 70. Upon a smooth white surface place 
 a small quantity of iron filings. Bring a soft iron bar in 
 contact with them and notice whether they attach them- 
 selves to its surface. Also bring a steel bar in contact 
 with them and observe whether they behave as before. 
 
 EXPERIMENT 71. Hold the end of the soft iron bar 
 among the filings and while it is there bring a permanent 
 
68 LABORATORY MANUAL 
 
 magnet in contact with the other end; observe whether or 
 not any filings cling to the iron bar. Remove the perma- 
 nent magnet and observe what takes place. Proceed in 
 the same manner with the hard steel bar. Does it support 
 as many filings as does the iron bar? Do they all drop off 
 on removing the permanent magnet? Try to magnetize 
 the iron permanently by rubbing it with the permanent 
 magnet, also try the same with the steel bar. Note the 
 results. What part of the bar will support the greatest 
 weight? (T. 86). 
 
 EXPERIMENT 72. Float a small magnetized steel bar 
 (a piece of watch spring answers very well) by means of 
 a flat cork in a flat porcelain dish nearly filled with water. 
 Notice that it comes to rest with its ends pointing north 
 and south. (T. 87). When the bar is at rest bring first 
 near its north end and then near its south end a bar of 
 soft iron. Notice in each case the effect on the magnet- 
 ized bar. Remove the end of the soft bar and see 
 
 
 
 whether the effect differs. 
 
 EXPERIMENT 73. With the steel bar, as in the pre- 
 ceding experiment, bring near its north seeking end first 
 one pole and then the other of a small bar magnet. 
 Notice that the pole that attracts the north seeking end of 
 the floating bar repels the south seeking end and vice versa. 
 Remove the bar from the cork and bring the end that 
 pointed north near either end of the galvanometer needle. 
 Notice that it attracts the south seeking end but repels the 
 north seeking end, behaving as did the bar in the first part 
 of the experiment. 
 
 EXPERIMENT 74. Magnetize a piece of watch spring 
 and after determining its polarity, break it in two and see 
 what relation the poles of one piece bear to those of the 
 other (T. 88, 89, 90, 91, 96, 97.). Is it possible to mag- 
 
OF ELECTROTHERAPEUTICS. 69 
 
 netize a watch spring in such a manner that it shall have 
 three or more poles? If so explain the process. 
 
 EXPERIMENT 75. Place a smooth piece of paper 
 over a bar magnet which is sunk beneath the surface of a 
 small board. Sift iron filings through a piece of cloth 
 evenly over the surface of paper and tap it lightly. The 
 filings will arrange themselves in well defined curved lines 
 around the magnet. Make a sketch of the magnetic field 
 thus shown. Also in like manner prepare and draw the 
 magnetic fields between two similar and two opposite 
 magnetic poles. What direction is attributed to magnetic 
 lines of force (i) within the magnet and (2) in the mag- 
 netic field? Can the number of magnetic lines of force 
 in a permanent magnet be varied by causing an armature 
 to approach or recede from it? (T. 375-377). 
 
 MAGNETIC EFFECTS OF THE ELECTRIC CURRENT. 
 
 The following are a few of the most important laws 
 relating to the magnetic effects of electric currents: 
 
 1. A piece of soft iron surrounded by a coil or helix 
 of insulated wire becomes a magnet and retains that 
 property while an electric current is flowing through the 
 helix. 
 
 2. The strength of an electro-magnet is proportional 
 to the strength of current and to the number of turns of 
 wire in the helix in other words, is proportional to the 
 number of ampere turns. This law is only true so long 
 as the iron core, is still unsaturated. 
 
 3. Upon interrupting the current in the helix the 
 magnetism induced in the iron at once disappears. Nearly 
 all specimens of iron retain a trace of magnetism for a 
 time, the amount retained and the time depending on the 
 quality of the iron. (T. 367, 368). 
 
7 LABORATORY MANUAL 
 
 4. If the iron core or bar be removed from the helix 
 the latter will act, while the current is flowing, like an 
 electro-magnet but to a much smaller degree than when 
 the core is present. If the core be made up of a large 
 number of small bars it will both receive and give up 
 its magnetic properties more readily. (T. 381, 382, 383, 
 
 384). 
 
 EXPERIMENT 76. Having a soft iron bar, wind 
 around it from one end to the other an insulated copper 
 wire. Having one end of the bar held in position near 
 some iron filings and a small bichromate cell connected to 
 the wires, observe what takes place upon making and 
 breaking the circuit. Again bring one end of the electro- 
 magnet near the galvanometer needle and on completing 
 the circuit notice that the north seeking end is either 
 attracted or repelled. (Avoid bringing it too near). What 
 is the polarity of the end presented? Present the oppo- 
 site end of the electro-magnet and see whether the result 
 differs. Rewind the bar in the opposite direction and 
 observe whether the polarity has been changed. You should 
 be able to deduce the law which shows the relation between 
 the direction of the current around the helix to the magneti- 
 zation produced. 
 
 EXPERIMENT 77. With the iron bar used before wind 
 the wire midway between the ends, using the same number 
 of turns and covering not more than one- third of the bar. 
 Compare the strength with that of the covered bar. This 
 can be done by allowing it to pick up small pieces of iron 
 or preferably by observing the deflection produced on the 
 galvanometer needle at a given distance. Place the coil 
 at one extremity of the bar and compare the result with 
 the preceding. In all cases the wire should be evenly and 
 closely wound around the bar, and in each case the plates 
 
OF ELECTROTHERAPEUTICS. 71 
 
 of the battery must be removed from the liquid as soon as 
 the observation is made. Why ? 
 
 EXPERIMENT 78. With the coil at one extremity of 
 the bar remove the wire, one turn at a time, and observe 
 each time the change in the strength of the magnet. 
 What are the constant and what the varying factors in 
 this experiment? 
 
 EXPERIMENT 79. Having the coil at one end of the 
 bar either replace the small battery by a large one or 
 introduce a resistance into the circuit without changing 
 the number of turns on the bar. Observe the variation 
 in the strength of the magnet. Would you expect it to 
 vary the same way in either case? 
 
 EXPERIMENT 80. Now with the soft iron bar and the 
 helix arranged as in the preceding experiment, bring one 
 extremity near some small iron nails. Notice that they 
 cling to it only as long as the current is flowing. Replace 
 the bar with one of harder iron and repeat, noticing 
 results. Finally use a steel bar in place of the iron and 
 compare results with those obtained with the other bars 
 (T. 381 to 385). 
 
 EXPERIMENT 8 1. Float the bar of magnetized steel 
 upon a cork, pass over and parallel to it a copper wire 
 connected to your voltaic cell so that you can cause a 
 current to pass through it. Is there any action mani- 
 fested between the "live " wire and the magnet when they 
 are not in contact? If so, to what is it due and what will 
 you call the force? Now pass the current beneath and 
 parallel to the needle and on closing the circuit notice in 
 what manner the deflection varies from that in the first 
 part of the experiment. What would be the effect of 
 changing the direction of the current in the wire? 
 
72 LABORATORY MANUAL 
 
 What two ways of reversing a deflection have you discov- 
 ered ? (T. 195, 196, 197). 
 
 EXPERIMENT 82. Modify the last experiment by 
 floating your galvanometer so that its coil stands at right 
 angles to its needle, which will be the case when the 
 needle points to 90 on the scale. Pass the wire over and 
 parallel to the needle. On completing the circuit notice 
 that the needle behaves as did the bar in the last experi- 
 ment. 
 
 EXPERIMENT 83. Having the galvanometer as in the 
 last experiment, wind a wire once around so that the 
 needle shall lie within the coil and observe whether the 
 deflection is increased. Increase the turns of the wire 
 and observe whether the deflection is increased with each 
 additional turn (T. 200). Use insulated wire in this 
 experiment. 
 
 EXPERIMENT 84. With your insulated wire form an 
 oblong coil 2x^ inches made of six turns. Connect its 
 terminals with the wires from your voltaic cell. Hold the 
 coil just above and parallel to the needle of the galvano- 
 meter. When the current is sent through the coil com- 
 pare the deflection produced with that in the previous 
 experiment using the same number of turns of wire. 
 How can you explain the result? The strength of current 
 in the two cases should be exactly equal. 
 
 EXPERIMENT 85. Place the galvanometer so that the 
 needle shall come to rest at 90. Now send the current 
 from a bichromate cell through the coil connected with 
 the B terminals and then without making other changes 
 reverse the direction of the current passing through the 
 instrument. Explain the action of the needle in the two 
 cases (T. 196). 
 
INDUCTION CURRENT INSTRUMENTS. 
 
 (T. 228, 229, 230). 
 
 The induction coil is an instrument designed to trans- 
 form an electric current of a low electro-motive force to 
 one of equivalent energy but having a relatively high 
 electro-motive force. 
 
 There are three quite distinct classes of induction 
 coils dirrering in construction according to the intensity 
 of current desired and in the methods of regulating and 
 controlling them. 
 
 1. The first type is a very large coil consisting of a 
 primary of very heavy wire designed to carry strong cur- 
 rents and a secondary coil consisting of thousands of 
 turns of very fine wire very carefully insulated in which 
 currents having thousands and even millions of volts of 
 electro-motive force are generated. The current from this 
 class of coil is comparable in intensity to that of the 
 static machine. They are used in various kinds of scien- 
 tific research and more recently they have been much 
 employed to illuminate Crookes tubes for the purpose of 
 producing Roentgen rays. Some of the larger of these 
 coils have furnished sparks as much as forty-two inches 
 in length. 
 
 2. To this class belong the coils used in physio- 
 logical research. They give only a short spark but admit 
 of a wide range of adjustment for modifying the character 
 of the current. They are constructed so as to permit the 
 secondary coil to be moved over the primary. They are 
 usually spoken of as Dubois-Reymond coils. 
 
 3. To this class belong all coils used in therapeutical 
 
74 LABORATORY MANUAL 
 
 work and spoken of as medical induction coils. The cur- 
 rent is practically the same as that produced by those of 
 the second class excpt that the former do not as a rule 
 admit of so wide a range and gradual change in the 
 strength and character of the current. Coils of this form 
 are often enclosed in a neat case containing a small bat- 
 tery, conducting cords, electrodes, etc., and constitute a 
 -convenient portable instrument for the physician's use. 
 
 THE SIMPLE LABORATORY INDUCTION COIL. 
 
 This instrument consists of a primary coil only, the 
 secondary coil being absent. It has sufficient binding 
 posts to attach the battery to it and electrodes are fur- 
 nished through which the induced current can be utilized. 
 The parts are simple and plainly visible in order that the 
 student may become familiar with its construction and 
 with the principles involved in its operation. The descrip- 
 tion of the physician's induction coil which follows in- 
 cludes all that need be said regarding the primary coil 
 and its currents. 
 
 EXPERIMENT 86. Attach a 4 volt battery to the sim- 
 ple coil and adjust the parts so that it shall be properly 
 excited. Study the mechanism and working principles of 
 the automatic interrupter. The following are some of the 
 points to which the student should give his attention: 
 
 1. Determine the various points for attaching elec- 
 trodes for applying the induced current. 
 
 2. Determine the time of flow and the direction of 
 the induced current, i. e. , whether it flows at the "make" 
 or "break" of the battery current. This is best done by 
 slowly moving the vibrator backward and forward by hand 
 and passing the current thus induced through the tongue. 
 
 3. Determine how the soft iron core becomes mag- 
 
OF ELECTROTHERAPEUTICS. 75 
 
 metized by the passage of the battery current. From the 
 principles of electro-magnetic induction what is the 
 direction (compared to that of the battery current) of the 
 induced E. M. F. when the core is becoming magnetized 
 .and when it loses its magnetic lines of force? 
 
 4. What do you think of the relative rates with 
 which the core takes up and loses its magnetic lines of 
 force? What is the effect on the E. M. F. of the primary 
 induced current of increasing the strength of the battery 
 current through the coil? 
 
 EXPERIMENT 87. Test for the effect of moving the 
 brass tube with respect to the iron core upon the E. M. F. 
 of the primary induced current. What is the effect where 
 you employ a tube with a slit along its entire length? Try 
 the effect of enclosing the primary coil in a cylinder of 
 metal and what results when the circuit in this cylinder is 
 broken? What is your explanation of the results of the 
 above observation ? 
 
 EXPERIMENT 88. Examine the electric bell and 
 notice the general similarity of its construction to that of 
 the interrupter of the coil. Notice the spark produced by 
 the extra current. Does it correspond to the primary 
 induced current of the coil? At what points would you 
 attach electrodes to the bell in order to send the current 
 through a patient? 
 
THE PHYSICIAN'S INDUCTION COIL. 
 
 To rightly understand the therapeutic capacities of 
 the faradic battery or physician's induction coil it is neces- 
 sary to start with a clear conception of the mechanism by 
 which the various currents derived from this apparatus are 
 produced. 
 
 The analysis of one of the simpler forms of induction 
 coil, such as is commonly employed by physicians will 
 best serve this purpose as it contains all the essential 
 elements entering into this form of apparatus. The more 
 elaborately constructed coils are but attempts to perfect 
 the working of one or more of the parts of which these 
 simpler or cheaper coils are composed. 
 
 The induction coil apparatus used for therapeutic 
 purposes must have 
 
 A primary battery, or other original source of current, 
 
 A primary coil, 
 
 A temporary magnet, 
 
 An interrupter, or circuit-breaking device, 
 
 A secondary coil, 
 
 Some means for varying the amount of current 
 induced in either coil. 
 
 Separate consideration will be given to each of these 
 parts. 
 
 The Primary Battery. In the ordinary portable 
 faradic battery one or two wet or dry cells furnish the 
 current which excites the induced currents in the coils. 
 The number and electro-motive force of these cells must 
 be proportionate to the resistance to be met with in the 
 coil circuits. When wet cells are used they are commonly 
 
OF ELECTROTHERAPEUTICS. 77 
 
 either the bichromate or ammonium chloride cells. The 
 electro-motive force of the former (1.9) is about one- 
 fourth higher than the latter (1.4), neither do they polarize 
 so quickly and therefore maintain a more constant cur- 
 rent. The dry cells are more convenient because of 
 being dry, but they cannot be renewed by the operator 
 but must, when exhausted, be replaced by new ones. 
 The composition entering into the various dry cells is a 
 trade secret, but those of larger size usually have zinc and 
 carbon elements with a paste containing ammonium 
 chloride as an excitant. The chloride of silver dry cell is 
 the most convenient because of its small size but its 
 electro-motive force (.9) is less than that of other forms 
 of dry cells. It requires from two to three volts pressure 
 to properly energize the ordinary induction coil apparatus, 
 and a dynamo current can be used to furnish this current 
 quite as well as a primary battery, but for portable bat- 
 teries this source of current for exciting the coils cannot 
 be utilized. With coils of greater resistance more electro- 
 motive force is needed in the circuit from which the 
 primary energy is obtained, and in case primary battery 
 cells are used to supply the current the number must be 
 sufficient to meet the requirements of increased resistance. 
 So it happens that in certain forms of induction apparatus 
 recently put upon the market, in which the secondary coil 
 contains a great many turns of very fine wire, four or 
 more primary battery cells are needed to properly energize 
 the coils. 
 
 The Primary Coil. The main purpose of the 
 primary coil is to furnish a path for the battery current 
 and to interrupt and transform that current in such a 
 manner as to create induced currents in a secondary coil 
 which is either wholly or but partially within its field of 
 
78 LABORATORY MANUAL 
 
 influence. To accomplish this purpose the primary coil; 
 need be made of but few turns of a comparatively coarse 
 wire; the main object being to offer but little resistance to- 
 the primary battery circuit. Our laboratory experimental 
 induction coils contain three turns of number 19 wire in 
 the primary coil, the outside diameter of the coil being 
 2 centimeters and its length 10 centimeters. There is, as 
 we shall presently see, a current possessing peculiar physi- 
 cal properties induced in this primary coil, which is utilized 
 for therapeutic purposes and called the primary current. 
 For the purpose of giving a different quality to this 
 primary current some manufacturers have increased the 
 number of turns of the primary coil and used wire of 
 different sizes. The battery current which traverses the 
 primary coil has for a part of its course a vibrator spring,. 
 Fig- 35> and a set screw and post which form very essen- 
 tial elements in the action of the induction coil apparatus 
 as will be seen later. 
 
 A Temporary Magnet. A soft iron bar or a bun- 
 dle of soft iron wires capable of being readily magnetized 
 by the passage of the battery current along the primary 
 coil and again promptly losing its magnetism as this bat- 
 tery current is interrupted, is the part of the induction 
 coil apparatus upon which its action chiefly depends. 
 
 The main purpose of the temporary magnet is to 
 break the battery circuit and so interrupt the flow of cur- 
 rent from the battery through the primary coil. This the 
 temporary magnet does the instant it becomes magnetized 
 through the influence of the current passing in the primary 
 coil which is wound about it. By its magnetic force it 
 attracts the iron head on the vibrator spring or interrupter, 
 Fig. 35, and draws away the spring from the point of 
 the adjusting screw (G) and so leaves a gap (M) in the 
 
d 
 
 ^ 
 
 P- 
 
 ;r 
 
 -C 
 <s> , 
 
 2 
 
 i 
 
 *n 
 
 a 
 
 Q 
 
8o 
 
 LABORATORY MANUAL 
 
 battery circuit. This stops the flow of the battery current 
 in the primary coil. The soft iron core then loses its mag- 
 netism and releases the head of the vibrator spring which 
 flies back and is again in contact with the point of the 
 adjusting screw. A second advantage gained by the 
 temporary magnet, if placed, as it is in many of the 
 simple forms of induction apparatus within the turns of 
 the primary coil, is an augmenting of the inductive effect 
 
 on the coils by reason 
 of the magnetic lines 
 of force emanating 
 from the magnet and 
 cutting the turns of 
 wire in the primary 
 and secondary coils. 
 In some of the Du- 
 bois-Reymond forms 
 
 Fig. ?6. Faradic Coil with Dry Cells. of induction coil the 
 
 temporary magnet is used only to interrupt the circuit of 
 the battery current and is placed at a distance from the 
 primary and secondary coils and so this augmenting in- 
 ducing action upon them is lost. 
 
 The Circuit-breaker or Interrupter. The cur- 
 rent that flows from the battery through the primary coil 
 must be broken or interrupted at intervals, since it is by 
 the change of potential in the circuit that is thus produced 
 that the induced currents in the coils are created. The 
 range of frequency of such interruptions is determined by 
 the kind of device that is used for producing them. In 
 the ordinary coils the interruptions are effected by a spring 
 at the extremity of which is an iron head ( H ), Fig. 35. This 
 bit of iron is alternately attracted to and released from the 
 temporary magnet. The rapidity with which interruptions 
 
OF ELECTROTHERAPEUTICS. 8 1 
 
 can be made by the mechanism varies greatly in different 
 instruments. It depends upon the strength of the mag- 
 netic flux, the readiness with which the magnet takes on 
 and gives up its magnetism, the length of the spring and 
 its elasticity. Seldom are any two instruments of the same 
 pattern alike in all of these particulars. The maximum 
 of interruptions that can be brought about in our ordinary 
 laboratory coils averages 60 per second, and these are a 
 fair sample of the induction coils in general use. By 
 greater attention to details in the construction of this and 
 other parts of the induction coil, as in the use of longer 
 and more nicely adjustable springs, and the use of a 
 quality of iron in the temporary magnet that will insure 
 the greatest promptness in response to the inductive 
 influence, the rapidity of interruptions by this method can 
 be considerably increased. But we have yet failed to find 
 an instrument with a spring vibrator in which the number 
 of interruptions can be made to reach 200 per second. 
 The number of interruptions in an induction coil current 
 is one of the important elements in producing physio- 
 logical and therapeutic effects, since the greater their 
 frequency the more the sharp and irritating quality of the 
 current is reduced, and the more soothing it is in its 
 influence. Numerous attempts have been made to secure 
 more rapid and uniform interruptions by other arrange- 
 ments than that of the spring vibrator, but so far the 
 devices have been either too complex or expensive to 
 create much demand for them. The Englemann segmented 
 rotary interrupter, run by an electric motor, is capable of 
 greatly increasing the number of interruptions and with 
 perfect uniformity, but its cost places it beyond the reach 
 of the majority of those using induction coils. 
 
82 
 
 LABORATORY MANUAL 
 
 Fig. 37. Form of Induction Coil, used in this 
 Laboratory. 
 
 The Secondary Coil. The secondary coil is the 
 induction coil proper, and the current derived from it can 
 be caused to vary considerably in strength and quality at 
 
 the will of the op- 
 erator. This coil is 
 always made of finer 
 wire than that used 
 in the primary coil. 
 It usually has a much 
 greater number of 
 turns also and the 
 length of the wire is, 
 of course, propor- 
 tionately increased. 
 In our laboratory ex- 
 perimental coils the 
 secondary is wound 
 with number 31 wire and has 3 layers, the length of wire 
 used being about 180 feet, the resistance of which is about 
 35 ohms. Most secondary coils for physicians' use are 
 now made of still finer wire. Number 36 is preferred by 
 many, and the number of layers is as many as eight or ten 
 or even more. 
 
 The finer the wire the greater the number of turns 
 made in each layer, and as each additional turn of wire 
 adds one to the frequency with which the lines of magnetic 
 force, emanating from the primary coil and the temporary 
 magnet, cut the secondary coil, and so increase the electro- 
 motive force of the secondary coil current, a great number 
 of turns in the secondary coil is by some thought desirable. 
 But there is a limit to the advantages to be gained by 
 lenghtening the wire and increasing the number of turns 
 in the secondary coil. The resistance of the amount of 
 
OF ELECTROTHERAPEUTICS. 83 
 
 wire used and of the self induction created in the coil may 
 prove too much for the primary battery current to over- 
 come and the resulting secondary induced current will be 
 very feeble. 
 
 Much of the efficiency of the faradic or induction 
 coil apparatus depends upon the nature of the secondary 
 coil current and as a different quality is required in this 
 current for different therapeutic purposes, some manu- 
 facturers provide several secondary coils with different 
 sizes and turns of wire. Others make a continuous 
 winding of the one size of wire but make this of consid- 
 erable length, and then tap the wire at intervals so that 
 the current from all or only a part of the coil can be used 
 as desired. The nature of this secondary current as com- 
 pared with the primary induced current will be considered 
 further on. 
 
 Current Regulation. Every induction coil appara- 
 tus is provided with some means for increasing or decreas- 
 ing the strength of the currents derived from it. This is 
 done by modifying the strength of the magnetic field that 
 induces currents in the coils. One of two ways is used 
 to do this. The coils are arranged, in the one case, to move 
 one over the other as in the Dubois-Reymond type of coil, 
 which is the form usually employed by physiologists for 
 their experimental work, and which produces very fine 
 and uniform gradations in the amount of current. Or a 
 metal shield of brass is made to slip over the temporary 
 magnet placed in the axis of the coils which shield, when 
 in place, attracts to itself the lines of magnetic force 
 emanating from the magnet and prevents them from 
 cutting across the turns of this coil. As the shield is 
 removed the lines of magnetic force are released and thus 
 induce currents in the coils in proportion to the extent to 
 
84 . LABORATORY MANUAL 
 
 which the magnet is uncovered. A crude method of 
 measuring the strength of induction coil currents is to 
 attach an inch or meter scale to the apparatus so as to 
 measure the position of this shield at any moment or in 
 the other case the extent to which one coil covers the 
 other. All the better instruments are provided with such 
 a scale. 
 
 NATURE OF THE INDUCTION COIL CURRENTS. 
 
 We must now, in order to judge of their therapeutic 
 applications, study the modalities of the electric currents 
 that are derived from the physician's induction coil. 
 When this apparatus is in action, it is capable of generat- 
 ing three distinct currents. 
 
 The battery current, 
 
 The primary induced current, 
 
 The secondary induced current. 
 
 The Battery Current. No attempt is made to use 
 the battery current in the induction coil apparatus for 
 therapeutic purposes. Its function is to supply an electro- 
 motive force in such manner as to create magnetic lines of 
 force in the temporary magnet and exercise an inductive 
 influence upon the coils. In order to effect this so as to 
 secure a succession of induction current impulses, the 
 battery current must be interrupted with more or less 
 frequency, as it is only by varying the number of lines of 
 force that cut across the coils that an induced current is 
 created in them. The "make" and "break" of the bat- 
 tery current, which is effected by the interrupter, is an 
 indispensable feature, therefore, in the induction coil 
 apparatus. And the frequency with which these inter- 
 ruptions in the battery current take place determines, im 
 a great measure, the nature and physiological and thera- 
 
OF ELECTROTHERAPEUTICS. 85 
 
 peutic effects of the induced currents which follow. The 
 battery current should be strong enough to saturate the 
 temporary magnet with a magnetic flux and to successfully 
 withstand the opposing electro-motive force which is 
 created by self-induction in the primary and secondary 
 coils when their circuits are closed. The larger the 
 temporary magnet and the greater the resistance and num. 
 ber of turns in the primary and secondary coils, the 
 greater will need to be the electro-motive force of the 
 
 Fig. 38. Induction Coil with changeable Vibrator. 
 
 primary battery used for furnishing this battery current. 
 The battery current (ABBBA') in Fig. 35, is, of course, a 
 direct or galvanic current, that is a uni-directional current, 
 but it is interrupted or broken as often as the spring (H) 
 is carried away from the contact (M). The E.M.F. of this 
 current depends upon the kind and number of cells used, 
 and the amount of current depends upon the resistance in 
 the circuit. The quantity of current may vary, therefore, 
 from half an ampere to several amperes, according to the 
 make-up of the apparatus. 
 
86 LABORATORY MANUAL 
 
 The Primary Induced Current. At the moment 
 the magnetic lines of force which emanate from the tem- 
 porary magnet as a result of the influence of the battery 
 current begin to cut the turns of the primary coil, an 
 electro-motive force is generated by them in the primary 
 coil, which is opposed to the flow of the battery current 
 and decreases it. When the battery current is interrupted 
 by the breaking of the circuit at the spring vibrator, the 
 inductive influence of this current on the temporary mag- 
 net ceases, and there is a sudden withdrawal of the mag- 
 netic lines of force which came from this source. 
 
 This sudden loss of potential creates an induced cur- 
 rent in the primary coil which has the same direction as the 
 battery current, but as the battery circuit is open between the 
 contact point and the spring, this current can only trav- 
 erse that circuit by leaping the air-gap, which it does at 
 times and causes the spark which is seen at this point 
 when the instrument is in action. If another circuit is 
 provided for this current that is induced in the primary 
 coil at the "break" of the battery current, then this in- 
 duced current at the "break" can be utilized in thera- 
 peutic work. And this is the origin of the current derived 
 from the medical induction coil that goes by the name of 
 primary current. It is a unidirectional current, (Fig. 39) 
 but interrupted with a frequency corresponding to the move- 
 ments of the vibrator. It has the same direction as the 
 battery current, but differs from it in having less of quantity 
 but higher electro-motive force. Both its strength and 
 electro-motive force can be varied by moving the shield 
 covering the core, or by changing the position of the core 
 itself, if this is made movable. 
 
 The primary induced current has in a feeble way the 
 properties of a direct or galvanic current. It is both elec- 
 
OF ELECTROTHERAPEUTICS. 87 
 
 trolytic and cataphoric to a slight degree, but its chief 
 action upon the living organism is as an excitant to con- 
 tractile tissue and to sensory nerves by reason of the inter- 
 ruptions which cause a sudden variation in potential. The 
 suddenness of this change in electro-motive force makes 
 this current a powerful stimulant for exciting muscular 
 contractions and for arousing the action of sensory nerves. 
 The Secondary Induced Current. The secondary 
 coilwinding(FFFF)(Fig. 35) wr/Vm 
 
 is entirely distinct from the j.c***** <?*"* 
 
 TTto 7>trZu.e.tiot*, 
 
 primary and has its separate 
 
 terminals at the binding- o * * 
 
 posts (EE'). In some forms /g 
 
 of induction coils the secon- IL, 
 
 .W4.'! .-..of 
 
 dary coil can be removed 
 from the instrument, and 
 these instruments are sup- 
 plied with several secondary 
 coils differing in size and 
 length of wire and in the s<*aiajjy **** 
 
 number of turns. There are 
 
 induced currents generated in the secondary coil both at 
 the "make" and "break" of the battery current. The 
 inductive effect on the turns of the seconday coil at the 
 "make" of the battery current is due to the lines of force 
 from the magnet cutting across them. This current is com- 
 paratively slow in its increase to the highest potential be- 
 cause of the somewhat gradual development of these lines 
 of force. The induced current at the "break" on the con- 
 trary because of the sudden withdrawal of these magnetic 
 lines of force, is more promptly developed to its greatest in- 
 tensity and, of course, in the opposite direction from the cur- 
 rent induced at the " make." The secondary coil current 
 
88 LABORATORY MANUAL 
 
 then is a to and fro, or alternating current (Fig. 39) with the 
 "break" a little greater in intensity but shorter in dura- 
 tion than the "make" current, while the frequency of the 
 alternations or the number of periods depends upon the 
 action of the vibrator or interrupter. The electro-motive 
 force in this current is determined by the number of turns 
 in the coil that are cut by the magnetic lines of force, and 
 the quantity of current is determined by the resistance 
 offered to its flow and the strength of the magnetic flux 
 which induces it. The electro-motive force, when a fine 
 wire of many turns is used in the secondary coil, is much 
 higher than that of the primary induced current, while the 
 amount of current is correspondingly much less. 
 
 The alternating character of this current prevents it 
 from being either electrolytic or cataphoric, while its 
 physiological effects depend very much upon the struc- 
 ture of the coil and the frequency of the alternations. 
 If the alternations are very frequent and the coil com- 
 posed of many turns of fine wire, the resulting current, 
 though interrupted, begins to resemble in physical pro- 
 perties a sinusoidal current. The approaches to and 
 departures from the highest and lowest potential in each 
 period is, by this construction, made more gradual and 
 the effect physiologically is stimulating and yet not irritat- 
 ing. Its effect, therefore, is tonic and at the same time 
 sedative on both motor and sensory nerves. 
 
 EXPERIMENTS WITH THE MEDICAL INDUCTION COIL. 
 
 Before proceeding with the following experiments 
 demonstrate the induction coil to the instructor in charge 
 of the laboratory. 
 
 EXPERIMENT 89. What currents does the physician's 
 induction coil furnish? Test the effect of removing the 
 
OF ELECTROTHERAPEUTICS. 89 
 
 draw-tube. What are the effects of increasing the battery 
 power? Pass the current through the body from arm to 
 arm. Bare the fore-arm and with pointed electrodes cov- 
 ered with absorbent cotton and moistened with a saline 
 solution and with the other flat electrode on the back of 
 the neck, cause contractions of each separate muscle of 
 the fore-arm with the weakest primary and then with the 
 weakest secondary current that will cause a contraction. 
 The pointed electrode should be placed over the point of 
 entrance of the nerve supplying the muscle. 
 
 EXPERIMENT 90. Determine by moving the vibrator 
 slowly back and forth whether the secondary current flows 
 both at the "make" and "break" of the battery current. 
 Is there any difference in the direction and intensity of 
 the impulses ? 
 
 EXPERIMENT 91. Send the secondary current through 
 the galvanometer which is considerably removed from the 
 coil, and notice if it causes any deflection of the needle. 
 Move the interrupter slowly by hand and see if there is 
 any difference. Determine by experiment whether either 
 the primary or secondary induced currents are capable of 
 effecting electrolysis. 
 
 EXPERIMENT 92. Using the large dissected coil? 
 study the effects of removing the secondary coil from the 
 primary and also the effect of varying the number of wires 
 which make up the coil. 
 
 EXPERIMENT 93. With the skeleton coil and a tele- 
 phone receiver notice the induction effect between two 
 simple coils. Observe the sounds on making and breaking 
 the circuit slowly and the effect of removing the core. 
 
THE MAGNETO-ELECTRIC MACHINE. 
 
 (T. 222, 223, 224, 461.) 
 
 The magneto-electric machine is a current generator 
 which was at one time quite generally used in therapeutics. 
 The form commonly employed consists of two coils of 
 fine wire, each having a soft iron core and mounted in 
 such a manner that they can be rotated near a permanent 
 horse-shoe magnet. In this manner the number of mag- 
 netic lines of force passing through the two cores is made 
 to change continually, their polarity also changing, and 
 corresponding currents are set up in the coils according 
 to the principles discovered by Faraday. The two coils 
 are so joined that the E. M. F. generated in each re- 
 enforces the other. In machines not employing a com- 
 mutator the current is alternating in nature, each rev- 
 olution of the coils corresponding to a single impulse 
 in each direction. The rate of alternation is consider- 
 ably slower than in the secondary induction coil current 
 and in the sinusoidal current. The variations of E. M. F. 
 are not so abrupt as in the induction coil although some 
 types are so constructed as to cause sudden variations 
 of the E. M. F. The current from the magneto-electric 
 generator may be represented graphically very much like 
 the sinusoidal current except that the undulations are much 
 less regular. In some machines of this kind the current is 
 made to flow all in one direction by means of a commuta- 
 tor. The current then resembles the direct or galvanic 
 current except that it is irregular both as to amount of 
 current and electro-motive force. 
 
OF ELECTROTHERAPEUTICS. 9! . 
 
 EXPERIMENT 94. Examine the various forms of 
 magneto-electric generators in the laboratory and be pre- 
 pared to demonstrate any of them to the instructor. Take 
 the current from one of them through your body from 
 hand to hand and compare the sensation to that produced 
 by the direct current (galvanic) and the induced current 
 from the induction coil (Faradic). Attempt to electrolize 
 a solution of copper sulphate with it. Determine the 
 nature of the current by passing it through the long coil 
 of your galvanometer. How can the current be regulated 
 in strength ? Is the current generated sufficient to heat a 
 cautery wire? Can it be used for cataphoric or electro- 
 lytic purposes on the body? 
 
 THE SINUSOIDAL CURRENT. 
 
 By a sinusoidal current is meant an alternating induced 
 current in which not only the rise and fall of potential or 
 electro-motive force of positive direction is immediately 
 succeeded, without break, by an exactly corresponding 
 rise and fall of potential of negative direction, but one in 
 which this rise and fall in both directions would, if shown 
 with accuracy in diagram, describe a sine curve. The 
 accompanying illustration, Fig. 40, taken from Prof. H. S. 
 Carhart's work on Elementary Physics, with the permission, 
 of the author, well illustrates this form of curve. 
 
 Mathematically considered this curve may be defined 
 as one resulting from two rectilinear motions at right 
 angles to each other; the one being a uniform rectilinear, 
 the other a simple harmonic motion. This last named 
 motion is one well illustrated by the common pendulum, 
 which moves most rapidly at the middle of its swing,. 
 
92 LABORATORY MANUAL 
 
 decreasing in -rapidity as it approaches the ends. The 
 figure represents diagramatically a combination of these 
 two motions. The equal spaces made by the vertical lines 
 at the right represent the progress of the uniform rectilinear 
 movement from left to right, while the spaces between the 
 horizontal lines represent the simple harmonic movement 
 or sine displacements. These spaces on the vertical lines 
 are obtained by dividing the circle at the left into 16 equal 
 -arcs and drawing horizontal lines through the points 
 marking their boundaries, as i, 2, 3, etc. Now if we 
 assume that this circle is made to revolve at right angles 
 
 10 p^gj 
 
 i, 
 
 \ 
 
 
 
 
 
 
 
 
 
 
 
 
 
 N 
 
 5 
 
 
 
 
 
 
 
 
 
 
 
 
 
 7 
 
 
 
 /\ \ * ' xN. 
 
 
 
 \ 
 
 
 
 
 
 
 
 
 
 
 1 
 
 
 
 
 \ 
 
 
 
 
 
 
 
 
 
 
 
 / 
 
 
 
 V 
 
 \\J ' *' \i 
 
 
 
 
 
 
 
 
 
 
 
 
 
 1 
 
 
 
 
 \ 
 
 
 
 
 
 
 
 
 
 
 
 / 
 
 
 
 \ 
 
 w i- 
 
 
 
 d 
 
 \ 
 
 
 
 
 
 
 
 
 1 
 
 
 
 
 
 
 \ 
 
 
 
 
 
 
 
 
 
 1 
 
 
 
 
 \| 
 
 L-<*:-,l 
 
 
 
 
 * 
 
 \ 
 
 
 
 
 
 
 1 
 
 
 
 
 
 
 
 
 \ 
 
 
 
 
 
 
 
 / 
 
 
 
 
 
 
 
 
 
 
 
 f 
 
 \ 
 
 
 
 
 J 
 
 
 
 
 
 
 
 
 
 
 \ 
 
 
 
 
 
 1 
 
 
 
 
 
 
 
 Sl 7 \^S 
 
 
 
 
 
 
 .'/ 
 
 v 
 
 
 
 > 
 
 
 
 
 
 
 
 
 
 
 
 \ 
 
 
 
 / 
 
 
 
 
 
 
 
 
 10g-^ 
 
 .. 
 
 n 
 
 ?. 
 
 n 
 
 jj 
 
 ' 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 Fig. 40. 
 
 to the plane of the paper with the line o, 5, e, for its axis, 
 one revolution of the circle will correspond to a complete 
 vibration of a pendulum, and if, while revolving, the 
 circle moves from left to right at a uniform rate along 
 the axis o, 5, e, then the displacement of any point upon 
 the margin of the circle from the middle line is propor- 
 tioned to the sine of the angle of rotation on the circle. 
 Thus if we take the point 5 and rotate it through the arc 
 5, 6, the vertical displacement of the point 5 will be the 
 sine of the angle of rotation 5, o, 6. Again the vertical 
 displacement from 5 to 7 is the sine of the angle 5, o, 7. 
 It will be seen that these sines correspond to vertical dis- 
 tances between the horizontal lines at the right of the 
 
OF ELECTROTHERAPEUTICS,. 93' 
 
 circle and that the diagonal lines in the parallelograms are- 
 but the resultant of these two movements of the circle. 
 
 The sine curve can be platted by completing these 
 diagonal lines through one entire revolution of the circle. 
 
 The current derived from the secondary circuit of am 
 induction coil, Fig. 35, has been shown to be alternating, 
 but the positive and negative alternations differ considera- 
 bly in electro-motive force and the gradations from zero 
 to the greatest difference of potential in either direction 
 are not regular and uniform but quite the contrary. 
 Moreover, the secondary current of the induction coil is 
 interrupted, the time interval occupied by the interruptions 
 exceeding considerably that consumed by the passage of 
 the current. In these respects the secondary current of 
 the induction coil differs from a sinusoidal alternating 
 current in its physical properties, and these physical differ- 
 ences have of necessity a corresponding difference in 
 physiological and therapeutic effects. By increasing the 
 length and number of turns of the secondary coil and 
 increasing the rapidity of the vibrations of the interrupter 
 the current derived from the secondary coil of the induc- 
 tion apparatus is made to approach more nearly in physical 
 and physiological properties the sinusoidal current as at 
 present used. 
 
 The magneto-electric apparatus, which has been 
 spoken of and which some years ago was not infrequently 
 seen in physicians' offices, likewise creates an alternating 
 current. But the alternating current generated by this- 
 little machine, while it shows no interruptions when the- 
 coils are revolving, is yet quite irregular as compared 
 with a sinusoidal current,, since the lines of magnetic- 
 force emanating from the poles of the magnet cut the- 
 turns of wire in the coils as. they revolve, in such manner 
 
94 LABORATORY MANUAL 
 
 as to create no uniformity in the increase and decrease of 
 the induced currents. It is, however, only in this feature 
 of construction that this well-known magneto-electric 
 machine differs from several of the sinusoidal machines 
 that are now being manufactured for therapeutic work. 
 In these latter the attempt is made, with more or less 
 success, to secure such uniformity in the increase and 
 decrease of the number of the magnetic lines of force 
 that cut the coils as they revolve, that the electro-motive 
 force generated will describe the sine curve. This desir- 
 able result is the more nearly attained according as the 
 permanent or electro-magnets used are so shaped as to 
 furnish to the coils a strictly uniform gradation in the 
 strength of the magnetic field as they enter and leave it. 
 Although the modern apparatus shows great progress in 
 skill and workmanship yet it is quite probable that no so- 
 called sinusoidal machine has yet been constructed that 
 describes accurately in its action the sine curve. 
 
 The alternating current dynamos now used so exten- 
 sively for lighting incandescent lamps furnish a current 
 which is roughly sinusoidal and can be utilized by physi- 
 cians who have access to it and have some form of con- 
 troller suitable for modifying its strength and voltage. As 
 the speed of these dynamos, while in action, is quite 
 uniform, the number of alternations do not vary much 
 and the frequency is often much less than is wanted in 
 therapeutic work, being often but 124 alternations per 
 second. It is convenient and oftentimes quite desirable 
 to have an apparatus for the generation of a sinusoidal 
 current so arranged that the operator can vary the fre- 
 quency of alternations, the electro-motive force and the 
 current at will, and this is possible with some of the 
 machines now manufactured, two forms of which will be 
 illustrated and described. 
 
OF ELECTROTHERAPEUTICS. 95 
 
 PHYSIOLOGY AND THERAPEUTICS OF THE SINUSOIDAL 
 CURRENT. 
 
 There are several physical peculiarities possessed by 
 the sinusoidal current which help to make its action on 
 the body different from that of other forms of current. 
 As has been seen from the foregoing description the 
 increase and decrease of potential in this form of current 
 is gradual and uniform and never abrupt nor sudden in 
 its change. It is no doubt to this feature of the current 
 that its peculiar action on the sensory and motor nerves is 
 mainly due. The sensory and motor mechanism of the 
 body is capable of adjusting itself to a considerable range 
 of difference in external conditions without serious dis- 
 turbance or discomfort, provided the change is not too 
 sudden or violent. Even though there may be many 
 periods of alternation of current per second and the 
 electro-motive force be quite high, yet the action of nerve 
 and muscle is still capable of responding to such varia- 
 tions without disagreeable reaction provided the change in 
 strength is gradual. The number of alternations per 
 second, the degree of electro-motive force and the quan- 
 tity of current are, no doubt, each important factors in 
 determining the physiological and therapeutic effects of 
 this current, but these are not so peculiar to it as is this 
 feature of uniformity in change. The effect of this spe- 
 cial feature of the sinusoidal current is to lessen the 
 disagreeable effects of electric excitations both on the 
 sensory and motor mechanism. The same amount of 
 stimulation to muscular action can be aroused as by any 
 other equally powerful means, without the accompanying 
 pain and consequently without the shrinking and appre- 
 hensiveness on the part of the patient which other forms 
 of excitation arouse. In this lies the chief advantage of 
 
96 LABORATORY MANUAL 
 
 the sinusoidal current over the current derived from the 
 secondary induction coil, while in many other respects 
 these currents are similar in action. 
 
 For exciting to vigorous action muscular tissue, 
 therefore, whether it be the voluntary or involuntary 
 variety of muscle, the sinusoidal is the current par excel- 
 lence. Such frequency of alternations can be used as will 
 adapt the excitation to the requirements of the muscular 
 structure. The comparative painlessness of the applica- 
 tions permits the use of greater electro-motive force and 
 more current than can be used either from the induction 
 coil or the primary battery, so that physiological action 
 of the muscles is more thoroughly aroused than by the 
 use of either of these other forms. The more nearly the 
 curve of current conforms to the sinusoidal the less will 
 there be of effects resulting from polar action. Electro- 
 lysis and cataphoresis will be avoided and the changes 
 brought about in the tissues to which the current is 
 applied will be mainly those which are normal to their 
 function; the effect of the current being to arouse that 
 function to greater activity. When we consider how 
 many of the normal processes of the body, such as assim- 
 ilation, circulation, secretion, excretion, locomotion, etc., 
 depend directly upon muscular tone and vigor it will be 
 seen at a glance what a wide range of therapeutic applica- 
 tion is possessed by this form of current in the field of 
 muscular excitation alone. It has been highly spoken of 
 by many competent electro-therapeutists as a means of 
 improving the nutrition and growth of muscular tissue 
 whenever it is failing from lack of proper excitation. 
 
 General muscular weakness, local paralysis or paresis, 
 lack of intestinal peristalsis, vaginal and rectal prolapsus, 
 due in whole or in part to lack of muscular tone, and 
 
OF ELECTROTHERAPEUTICS. 97 
 
 vasomotor debility are some of the conditions in which 
 this form of current has proved especially beneficial. 
 
 It has been said that the sinusoidal current is remark- 
 able for the little amount of sensory excitation it causes, 
 and so permits powerful muscular contractions without 
 discomfort. Further than this it serves to allay pain. It 
 is as much if not more serviceable in this way than is the 
 current derived from the secondary induction coil of many 
 turns. Apostoli and others have borne strong testimony 
 to the fact that the greatest success they have attained 
 with this form of current has been in allaying the pains 
 that occur in connection with the pelvic organs. The 
 pains caused by uterine inflammation, pelvic cellulitis, 
 ovaritis, salpingitis and congestion are quickly allayed by 
 it. Neuralgic pains are relieved and those of spinal irri- 
 tation. Marked effects on tissue metabolism have been 
 noticed also as indicated by increased consumption of 
 oxygen and more rapid elimination of carbon dioxide. 
 These effects are in all probability secondary to and 
 dependent upon the increased muscular activity and 
 analgesic influence of the current. 
 
 THE Me INTOSH SINUSOIDAL APPARATUS. 
 
 This instrument, Fig, 41, is one result of the most 
 recent attempts by manufacturers to provide a source of 
 sinusoidal current for therapeutic work. It consists of a 
 small motor wound for the no direct current and has con- 
 nected with it a special rheostat for controlling its speed. 
 The shaft of the motor is extended and carries on this 
 extension the armature of the sinusoidal machine, thus 
 making a very convenient and compact arrangement, 
 doing away with belts and pulleys. The armature carry- 
 ing the winding of the coils of wire in which the induced 
 
9 8 
 
 LABORATORY MANUAL 
 
 sinusoidal currents are generated revolves between the 
 poles of a group of three powerful permanent magnets, 
 the pole pieces of which are so shaped as to secure a 
 uniform gradation in the lines of force which cut across 
 the revolving coils on the armature. From the coils the 
 current is conveyed to binding posts on the base of the 
 instrument, but before the current reaches the binding 
 posts a graphite rheostat is interposed regulating the 
 
 Fig. 41. 
 
 strength of the current. This arrangement makes the 
 apparatus complete It is only necessary to connect the 
 binding posts on the top of the motor with a suitable 
 direct current circuit such as the Edison incandescent 
 light circuit, or a street car or power dynamo circuit of 
 higher voltage, provided sufficient lamp resistance is 
 introduced so as to reduce the potential, and then com- 
 plete the patient's circuit by attaching electrodes to the 
 binding posts on the base. The rapidity of alternations 
 and consequently the voltage is readily modified by the 
 
OF ELECTROTHERAPEUTICS. 99 
 
 rheostat in the motor circuit while the strength of current 
 can be graduated independently by means of the rheostat 
 in the patient's circuit. Two additional brushes are in 
 contact with a commutator on the outer end of the arma- 
 ture shaft and these serve to deliver the current generated 
 as a current in one direction, instead of an alternating 
 one, when this is desired. The direct current so produced 
 can be thrown into the patient's circuit by a proper move- 
 ment of a switch which is provided on the base. By 
 connecting the motor of this instrument with a power cir- 
 cuit in this laboratory, the current supplied to the motor 
 registering by a Weston meter 120 volts, we were able to 
 run the armature shaft at the speed of 5280 revolutions 
 per minute when all resistance was off the motor circuit. 
 The number of alternations would of course be twice this, 
 or 10560 per minute; or 176 per second. By diminishing 
 the speed of the motor any less number of alternations 
 per second could be obtained. The strength of current 
 could be modified from that which was barely perceptible 
 up to that which would produce the most powerful muscu- 
 lar contractions, and yet at no time was the sensation pro- 
 duced, either in the integument or muscles, disagreeable 
 or painful as is so often the case with the current from the 
 faradic coils. The electro-motive force that is developed in 
 the patient's circuit depends upon the speed with which the 
 armature is made to revolve. At the highest speed attain- 
 able the Weston alternating voltmeter registered no volts 
 and at the slowest speed, 33 volts. If a lower electro- 
 motive force with great frequency of alternations is desired 
 this could be readily accomplished by having a less num- 
 ber of turns in the armature winding. 
 
 The direct or galvanic current that is furnished by this 
 instrument is of course not uniform in potential but varies 
 
100 LABORATORY MANUAL 
 
 in intensity at each revolution of the armature. With this 
 also the speed determines the amount of current. The 
 milliampere-meter showed this current to be 10 milliam- 
 peres at high speed, and when a patient was between the 
 electrodes and the direct current was carried up to the 
 limit of tolerance the amount of current was between 
 three and four milliamperes. Electrolytic work was 
 readily done by the direct current but the comparatively 
 high electro-motive force that was required to get sufficient 
 current for electrolysis might in some instances in actual 
 practice prove disagreeable to a patient, and the direct 
 current derived from this apparatus cannot be made to 
 take the place entirely of a galvanic battery or other 
 sources of direct current. 
 
 THE KENNELLY SINUSOIDAL MACHINE. 
 
 This machine (Fig. 42 ) bears a striking resemblance to 
 the ordinary multi-polar alternating current dynamo, but on 
 closer examination it will be found that both the primary 
 (exciting) and the secondary windings are placed upon the 
 field frame. The field frame is of laminated iron sup- 
 ported by castings and has twelve poles; on each pole is a 
 spool with two windings of wire. The inner has eight 
 layers of fine wire and the outer two layers of coarse wire. 
 All the coarse wire windings are connected in series in 
 such a way that the magnetic polarity produced shall be 
 alternately north seeking and south seeking, when a direct 
 current is sent through this circuit. 
 
 The armature is composed of several discs of sheet 
 iron firmly fastened together, having slots and projections 
 as will be seen from the figure. This armature is just 
 large enough to rotate freely within the concentrically 
 arranged pole pieces. Bearing in mind the relation of the 
 
OF ELECTROTHERAPEUTICS. 
 
 IOI 
 
 secondary coil to the pole, it is evident that anything 
 causing an increase or decrease of magnetic lines of force 
 through the pole, /'. e., any variation of the magnetic flux, 
 will induce a current of electricity in the secondary. The 
 E. M. F. of this induced current will depend upon the 
 number of turns of wire and the rate of increase or 
 decrease of the magnetic flux. In this machine the direct 
 
 Fig. 42. 
 
 current passing through the coarse wire windings consti- 
 tutes the magneto-motive force; this remaining constant, 
 the magnetic flux will vary inversely with the reluctance, 
 /. e., the "magnetic resistance." 
 
 The law of the magnetic circuit may be stated as 
 
 follows: 
 
 magneto-motive force 
 
 magnetic flux = - 
 
 reluctance. 
 
 The reluctance of air being very great as compared 
 with that of iron it follows that the magnetic flux in any pole 
 
102 LABORATORY MANUAL 
 
 will be suddenly increased when the air-gap or slot oppo- 
 site that pole is displaced by the iron projection of the 
 rotating armature, thus inducing a current in one direction 
 and the next instant when the wire projection is passing 
 and the next slot is coming opposite the pole there will be 
 a decrease of magnetic flux and a corresponding current 
 in the opposite direction. 
 
 The slots and projections of the armature are so 
 proportioned that the graphic representation of these 
 alternations of the current closely approximate the true sine 
 curve, thus giving the so-called sinusoidal current. 
 Twenty-four alternations or twelve complete periods occur 
 at each revolution of the armature; a speed of 80 revolu- 
 tions can be attained and will therefore give 1920 alterna- 
 tions per second or a frequency of 960. 
 
 The E. M. F. of the secondary current varies with 
 the amount of current flowing in the primary, /. <?., with 
 the magneto-motive force. This fact offers a convenient 
 method for regulating the voltage of the secondary with- 
 out varying the speed. The primary current may be 
 derived from primary batteries or from street mains and 
 should be passed through a rheostat so that it may be 
 varied from two amperes to the small fractional part of 
 an ampere. 
 
 The E. M. F. when the secondary is open varies 
 directly with the speed and the strength of current in the 
 primary circuit. With one ampexe in the latter circuit, 
 the limit of E. M. F. in the secondary is about 50 volts, 
 which is about 70 volts at the top of each wave, the 50 
 volts representing the average electric pressure. On short 
 circuiting the secondary, the voltage is reduced nearly to 
 zero, but in practice this will not occur except by accident. 
 The E. M. F. of the secondary passing through the body 
 
OF ELECTROTHERAPEUTICS. 103 
 
 of a patient will vary with the resistance offered, but 
 since this resistance is always comparatively high the 
 E. M. F. will practically amount to that recorded by a 
 voltmeter in open circuit. 
 
 In comparing this machine with others built for the 
 same purpose the following are some of the facts to be 
 considered: 
 
 The Kennelly machine requires both a motor for 
 running and some independent source of direct current 
 for exciting the fields. Neither of these are necessarily 
 disadvantages as the physician may possess these 
 accessories, and if he should not they may be procured at 
 a cost probably not exceeding that of those furnished with 
 other machines. Further, as has been shown, the inde- 
 pendent exciting current can be so controlled as to vary 
 the E. M. F. of the secondary without affecting the rate 
 of alternations. This is a decided advantage and one not 
 possessed by some other machines which we have exam- 
 ined. Again, it has the very desirable high rate of alterna- 
 tions attained by few others and which can be varied by 
 the motive power employed without materially changing 
 the voltage. 
 
 EXPERIMENT 95. Attach hand electrodes to the var- 
 ious forms of apparatus in the laboratory for generating 
 the sinusoidal current and take the current through the 
 body. Test the effect of varying the speed at which the 
 machines are run and also of varying the action of the 
 other controlling devices. Compare the sensation exper- 
 ienced with that produced by the induction coil currents 
 and also with that generated by the magneto machines. 
 Pay special attention to the physical characteristics of 
 the various alternating currents and to their physiological 
 effects. 
 
THE INDUCTION TRANSFORMER FOR CAUTERY. 
 
 (T. 224, 228.) 
 
 The instrument here described (Fig. 43) is one de- 
 signed to change the ordinary alternating current used in 
 lighting circuits to a current which is better adapted to meet 
 the conditions found in a cautery circuit. It has been seen 
 that a current in one system is capable of 
 setting up a current in another system near 
 it by induction. This is accomplished by 
 the rapidly changing magnetic field of the 
 primary system which extends to the sec- 
 ondary system. A current is thus set up 
 in the secondary coil which exactly corres- 
 ponds in the rate of alternation to that in 
 the primary. Except for a certain loss in 
 the transformation, the electro- motive 
 forces of the two systems will be propor- 
 tional to the number of turns of wire in 
 each. Further, the strengths of current in the two sys- 
 tems will be so related that the energy (C E = E) of the 
 one will equal that of the other. When the secondary coil 
 has fewer turns than the primary the E. M. F. will be 
 reduced and this is called a "step down" transformer. 
 
 The conditions required in a current .for heating a 
 cautery are such as demand a large current at a low 
 E. M. F. , and these conditions are met when the secondary 
 coil is made of few turns of heavy copper wire. The 
 strength of current is nicely regulated by sliding the sec- 
 ondary over the primary coil. By this method the control 
 of the current is so perfect as to render a cautery rheostat 
 in circuit entirely unnecessary. 
 
 Fig. 43. 
 
HIGH POTENTIAL, HIGH FREQUENCY 
 CURRENTS. 
 
 Currents of high tension and of great frequency of 
 alternations have long been known to the electro-thera- 
 peutist who is familiar with the action of the static machine. 
 The discharge which takes place between the prime con- 
 ductors of such a machine, when they are supplied with 
 Leyden jars or condensers, is at times of this nature. 
 During the small fraction of a second required for such 
 discharge, which may be spoken of as an instantaneous 
 current, the electric polarity changes many thousand times, 
 in oscillations of gradually diminishing amplitude. When 
 the arrangements during a treatment with the static 
 machine in action is such as to make the patient on the 
 insulated stool the terminus of the charge from one of the 
 condensers, and a ball electrode connected to the other 
 condenser is brought sufficiently near the person of the 
 patient to permit a spark to pass, /. e. , the direct or indi- 
 rect treatment by sparks, then, provided the relation of 
 capacity to resistance is just right, the patient is subjected 
 to a current of high frequency and high potential for the 
 instant corresponding to each discharge. Again, the 
 static machine may give rise to high frequency, high 
 potential currents in what has been termed the static induced 
 circuit, a current that is obtained in a circuit connecting 
 the outer surfaces or armatures of the Leyden jars or con- 
 densers. The patient may be made a part of this circuit 
 and so be subjected to the influence of these high poten- 
 tial, high frequency currents. 
 
106 LABORATORY MANUAL 
 
 But as one of the important features of this peculiar 
 electric modality in its relation to physiological and thera- 
 peutic action is the oscillatory character of the discharge, 
 the static machine as it is customarily employed cannot be 
 depended upon with certainty to furnish a discharge of 
 this nature. Whether or not the spark discharge of the 
 static machine is* impulsive or oscillatory in character 
 depends upon the relation which the capacity of the 
 machine and condensers bears to the inductance and 
 resistance of the circuit, and as certain of these terms 
 vary from time to time, due to atmospheric conditions and 
 manner of application the physical nature of the discharge 
 likewise varies, and therefore the static machine, in the 
 arrangement of its parts as now employed in therapeutics, 
 does not furnish the high potential currents with such 
 invariable regularity in number and frequency of the 
 oscillations as is required for accuracy in scientific observa- 
 tions and comparison of results. 
 
 If the output of electric energy from the static 
 machine was stabile and uniform the capacity of the con- 
 densers could be so adjusted to the resistance and induc- 
 tance in the circuit as to secure constancy in the oscillatory 
 nature of the discharge from them, but the obstacles to 
 this end have not yet been overcome. 
 
 Other sources than the static machine have therefore 
 been sought for and developed for generating high poten- 
 tial, high frequency, currents. Tesla, Elihu Thomson and 
 d'Arsonval have each been active in this search, and each 
 in his independent line of investigation has made use of 
 large induction coils as step-up transformers of the original 
 electric energy, which in some instances is derived from 
 alternating dynamos of low frequency and in others from 
 some direct current source, as a dynamo, a primary or 
 
OF ELECTROTHERAPEUTICS. 
 
 107 
 
 secondary battery. The low frequency of the alternating 
 dynamo must be changed to a high frequency, and the 
 constant or direct current must be broken up into sud- 
 den impulses with interruptions in order to furnish the 
 
 T W c\ vv c V \ (> YV Co \ 
 
 Fig. 44. 
 
 proper variations for inducing currents in the windings of 
 the induction coil. These necessities give rise to some 
 peculiarities in mechanism which have been variously con- 
 structed by the different inventors. The underlying prin- 
 ciples by which the ultimate result is secured are the same 
 
108 LABORATORY MANUAL 
 
 in all. The accompanying diagram (Fig. 44) will illus- 
 trate the various steps in the process. 
 
 B C D is an induction coil or transformer whose pri- 
 mary coil is energized from some source, preferably an 
 alternating current dynamo. If the- energizing current is 
 a direct current source then the primary circuit would 
 need to be supplied with an interrupting device to break 
 the current into periods, such as the spring vibrator 
 attached to the ordinary induction coils or, what is better, 
 a rotating disk driven by a motor and so arranged as to 
 make and break the circuit with great rapidity and sudden- 
 ness, as in the method devised by d'Arsonval. With the 
 primary coil excited in either manner named, induced 
 currents are created in the secondary coil D, the terminals 
 of which are joined to the internal armatures of two con- 
 densers or Leyden jars G G', between which is arranged a 
 spark gap F. The external armatures of the condensers 
 H H' are joined through a solenoid J of copper wire large 
 size and about 20 turns. When this system is in action, 
 at each break or alternation in the primary circuit, the 
 E. M. F. induced in the secondary coil charges the con- 
 densers. In proportion to the charge the difference of 
 potential between the armatures increases. When it 
 reaches the limit of the area of the ball terminals and the 
 space separating them at the spark-gap, which may be 
 many thousand volts, a discharge takes place across the 
 air gap and oscillates between the condensers, while the 
 solenoid J is traversed by a current of a frequency corres- 
 ponding to the frequency of the oscillations. These oscil- 
 lations are prevented from discharging into the circuit of 
 the secondary coil because of its great self induction. 
 When operating the system by energizing it from an 
 alternating dynamo circuit the charging and discharging of 
 
OF ELECTROTHERAPEUTICS. 
 
 the condensers is so frequently repeated that an arc is 
 likely to form across the spark gap and so put an end to 
 the oscillatory nature of the discharge. In order to pre- 
 vent the formation of this arc Tesla and Thomson em- 
 ployed first, a strong magnetic field and later, an air blast 
 at the spark gap. 
 
 When we compare the action of this system when ener- 
 gized by the alternating dynamo current, or the interrupted 
 direct current, we find that with the first the inductive 
 effects of the two waves of positive and negative potential 
 are the same, so that when the alternation has a frequency 
 of 124 periods per second as is customary with the 
 ordinary alternating dynamo used for industrial purposes, 
 there will be double the number or 248 single inducing 
 waves each second. With the direct current interrupted a 
 current effective in charging the condenser is induced in 
 the secondary only at the instant of "make," so that to 
 have the same number of useful waves as with the alter- 
 nating dynamo current, it would be necessary for the in- 
 terrupter to produce 248 contacts per second. 
 
 The currents that traverse the solenoid induced by 
 the discharge of the condensers to the outer armature of 
 which the solenoid is connected are those that are ordin- 
 arily utilized for therapeutic purposes. By connecting 
 conductors to each end of the solenoid a circuit can be 
 provided through which these currents can be conveyed. 
 This may be termed the patient's circuit, for it is to the 
 current generated at this point that the patient is, in one 
 or the other manner, subjected. 
 
 By an additional device, that is another step-up trans- 
 former, these currents may be brought to generate others 
 of still higher tension. These have been termed " cur- 
 rents of second order, M and are obtained by having the- 
 
110 LABORATORY MANUAL 
 
 solenoid of sufficient diameter to permit of placing within 
 it a glass tube enclosing a coil of fine, well insulated wire, 
 of many turns but a single layer. Currents of such ex- 
 tremely high potential are excited in this inner coil when 
 the solenoid is excited that the glass -tube surrounding the 
 coil of fine wire needs to be filled with oil to serve as an 
 insulator. The terminals of this fine wire coil brought out 
 at the extremities of the glass tube through proper stop- 
 pers can then be connected up in any manner desired so as 
 to exhibit the nature of these " currents of second order." 
 Hertz, Tesla and Thomson have each devised a num- 
 ber of beautiful and striking experiments by which to de- 
 monstrate the energy possessed by these high frequency 
 and high potential currents. It was early discovered that 
 they failed to excite the animal organism either in the 
 form of sensation or muscular movement, and yet after 
 traversing the body they render lamps and vacuum tubes 
 incandescent, and in many ways exhibit an expenditure of 
 electric energy which if applied to the animal body in 
 one of many other forms would prove instantly destructive. 
 
 ESSENTIAL PROPERTIES OF HIGH POTENTIAL HIGH FRE- 
 QUENCY CURRENTS. 
 
 As pointed out by Bordier, these currents are distin- 
 guished from ordinary alternating currents by three essen- 
 tial properties, 'which are due to both the great frequency 
 and the high tension. 
 
 ist. They cause remarkable inductive effects. 
 
 The E. M. F. of induction near an inducing source is 
 equal to the product of the intensity of the current by the 
 frequency. Let us suppose a frequency of 500,000 periods 
 per second and a mean current of i ampere. The E. M. 
 F. in one turn would be the same as if a current of 100 
 
OF ELECTROTHERAPEUTICS. 
 
 Ill 
 
 amperes with a frequency of 50 should circulate in 10 
 turns of wire. Thus it is seen that with high frequency the 
 E. M. F. induced in a single turn would be considerable. 
 In a large solenoid the current induced in one turn is suf- 
 ficient to illuminate by mutual induction a lamp of 8 volts 
 and i ampere. 
 
 2nd. Currents of high frequency, even though the 
 capacity be small, circulate as well in open as in closed 
 circuits, so that contact with only one pole suffices to give 
 a current 
 
 Fig. 45. 
 
 In fact, feeble as may be the capacity, the charge and 
 discharge, repeated hundreds of thousands of times per 
 second at a high potential, represent a notable mean cur- 
 rent. 
 
 It is this that explains the uni- polar currents, and the 
 sparks that occur when any point on the solenoid is 
 touched. In this case the body, constitutes an insulated 
 surface which, at each oscillation, is charged with a very 
 nearly constant quantity when it is at a certain .distance 
 from the solenoid. 
 
 The corresponding charge of contrary sign should be 
 
112 LABORATORY MANUAL 
 
 found on the parts of the solenoid which are at that 
 moment at a different potential. This explains why the 
 sparks which are drawn from the solenoid are greatest at 
 the extremities and least midway. 
 
 3d. The resonant effects, which have been so beau* 
 tifully shown by the experiments of Hertz, and which are 
 extremely interesting to the physicist, but which have not, 
 so far, been found to have any relationship to therapeutics. 
 
 METHODS OF APPLICATION. 
 
 In bringing the action of these high frequency cur- 
 rents to bear upon the human and other animal organisms 
 three methods of application have up to this time been 
 employed suggested by the properties of the current 
 which we have enumerated. 
 
 i st. Auto-conduction. In this mode of application 
 the capacity of the current to induce currents in objects 
 brought within their range, is utilized. In place of the 
 small solenoid above described a much larger one is em- 
 ployed, composed of well insulated cable wire, and wound 
 about a frame work capable of admitting into its interior 
 the man or animals to be treated. Although the person 
 enclosed in the solenoid is not in contact with it at any 
 point, nevertheless, while it is in action, induced currents 
 of extreme energy and frequency of oscillations are 
 induced in his body. These induced currets have their 
 seat in the organism itself and act upon the central nervous 
 system and deep seated organs and tissues as is shown by 
 the effects produced and recorded in the following article 
 on the physiological action of these currents. 
 
 2nd. The direct application. This is made by con- 
 ducting the currents generated in the small solenoid, or the 
 currents of second order, to any part of the body by 
 
OF ELECTROTHERAPEUTICS. 113 
 
 means of conducting wires and metallic electrodes and 
 thus making the body as a whole, or any part of it, as the 
 case may be, a part of the circuit. 
 
 3rd. Insulation. In this method the patient, person 
 or animal, to be subjected to it is placed upon an insulated 
 platform and connected by a wire to one extremity of the 
 solenoid while a point, -metallic point or plate, at some 
 little distance from the insulated platform is connected 
 with the other extremity of the solenoid. The person 
 acted upon is thus, as it were, made to take the place of 
 one of the armatures of a condenser and is subjected to a 
 charge which is slowly discharged by connection across 
 the interval between the body and the conductor leading 
 to the other extremity of the solenoid. 
 
 PHYSIOLOGICAL ACTION OF HIGH TENSION, HIGH FRE- 
 QUENCY CURRENTS. 
 
 This form of electric modality, except as it is fur- 
 nished by static or influence machines has not so far been 
 studied in its relation to physiological action by many 
 persons. Several notable electricians as Nikola Tesla,. 
 Elihu Thomson and Hertz have done much to acquaint us 
 with the apparent harmlessness of this form of electricity 
 when the living animal body, or some part of it, is made 
 the path of its transit. But to d'Arsonval and his assist- 
 ants the credit is mainly due for having determined with 
 scientific exactness and demonstrated by unquestionable 
 proofs that this electric modality does in many ways- 
 modify physiological processes most profoundly. While 
 we have for a number of months been using this form of 
 electricity in this laboratory, as generated by both the 
 Tesla and the Thomson forms of apparatus, we have, so 
 far, done little with it other than to confirm many of the 
 
114 LABORATORY MANUAL 
 
 results that d'Arsonval has reached and which he has pub- 
 lished from time to time in the transactions of the Societe" 
 de Biologic and of the Socie"te" Internationale de Physique. 
 
 What is set forth here, therefore, as the result of 
 investigation as to the relation of this form of electricity 
 to physiological action in the animal body, and which may 
 be regarded as fully established by abundant experiment, 
 is given mainly on the authority of d'Arsonval, and to the 
 detailed reports of his researches we would refer any who 
 may wish to examine into the data upon which the follow- 
 ing conclusions are based: 
 
 i st. The most singular and striking effect of high- 
 tension, high-frequency currents is their entire absence of 
 action on sensation. This is daily demonstrated in this 
 laboratory. When the Tesla apparatus is excited by an 
 alternating dynamo current and is pouring forth a torrent 
 of sparks between the terminals, across an air gap of eight 
 or ten inches, one can grasp these terminals, one in each 
 hand, and take the entire current through the body with- 
 out experiencing the slightest sensation except, perhaps, 
 one of gentle warmth at the wrists when the current 
 reaches, or exceeds three amperes. To demonstrate the 
 actual energy that is being expended during this proced- 
 ure it needs only to have two persons grasp these term- 
 inals each with one hand and then complete the circuit by 
 taking several incandescent lamps in series between them, 
 when the lamps, requiring each an ampere of current and 
 TOO or more volts to light them, will glow brilliantly while 
 the current is passing. 
 
 When the current is caused to impinge upon a limited 
 surface of the skin or mucous membrane in the manner 
 which in treatments by the static machine is termed "the 
 breeze " the part is soon benumbed and for a few moments 
 
OF ELECTROTHERAPEUTICS. 115 
 
 experiences the loss of sensibility which may go on to 
 complete anaesthesia. This insensibility does not pene- 
 trate deeply and lasts only a few moments, but that it may 
 be made to serve important therapeutic needs is at once 
 evident to a physician. 
 
 2d. These currents do not excite muscular contrac- 
 tions. Just as the passage of these currents through the 
 organism fails to arouse sensation so likewise motor nerve 
 and muscle are irresponsive to them. While the same 
 quantity of electric energy transmitted under the form of 
 alternating currents of long periods (100 10,000) and 
 much less voltage, would have caused violent muscular 
 contractions, which of themselves would suffice to kill the 
 recipient, here no contraction whatever occurs. 
 
 But just as a sensory nerve when subjected to the 
 direct action of these vibrations for a time is rendered 
 anaesthetic, so a motor nerve may be influenced in such 
 manner by these currents as to be for a brief period (10 
 to 15 minutes) incapable of responding to any form of 
 excitement. 
 
 3d. The high-tension, high-frequency currents im* 
 part an extraordinary activity to nutritive changes and to 
 cellular life. 
 
 This has been demonstrated. 
 
 (a) By examining and estimating in man and ani- 
 mals the products of respiratory combustion before and 
 after the action of the current. The oxygen absorbed is 
 seen to be increased considerably and carbon dioxide is 
 eliminated in greater quantity. 
 
 (b) By the amount of urea being greatly increased 
 in quantity, as has been determined by hundreds of uri- 
 nary analyses. 
 
 (c) By an increased heat production, which has 
 
Il6 LABORATORY MANUAL 
 
 been carefully determined by an ingenious anemo-calori- 
 meter devised by d'Arsonval. By this instrument it has 
 been established that by comparing the heat put forth by 
 the human body before and after this method of electriza- 
 tion, it is found to raise it from 79.6 cal. to 127.4 cal. per 
 hour at an average temperature of 17 C. 
 
 (d) By a loss of weight in the men and animals 
 experimented on during the period of application. This 
 would of necessity be the primary result of the increased 
 combustion. But it was found that in the intervals be- 
 tween the applications of the current there was a rapid 
 gain in weight. 
 
 4th. While there is no perceptible action of these 
 currents on the nerves of general sensibility and of volun- 
 tary muscle, the vaso-motor nervous system which con- 
 trols the vascular system is influenced by these currents to 
 a marked degree. The blood vessels in the ear of the 
 rabbit are seen to dilate rapidly under its action and this 
 is followed a little later by energetic contraction. The 
 same results take place in man as determined by the 
 sphygmograph and sphygmomanometer. The blood pres- 
 sure is at first lowered and after a little time rises and 
 remains elevated. 
 
 5th. Action on unicellular organisms. In order to 
 determine the direct action of these high-frequency, high- 
 tension currents on cellular physiology many forms of 
 bacilli were subjected to their influence. The cultures of 
 the pyocyanic bacillus were very much attenuated at the 
 end of some minutes. The chromogenous function is 
 first suppressed and if the experiment is continued for 
 half an hour the baccilli are killed. 
 
 The action of these currents is found to modify also 
 the products of the secretion of bacteria. The microbic 
 
OF ELECTROTHERAPEUTICS. Iiy 
 
 toxines are found to readily lose their virulence when sub- 
 jected to this electric modality for a short time. 
 
 D'Arsonval and Charrin have carried on a series of 
 experiments for some months to determine the modifying 
 action of various forms of electricity on the growth and 
 behavior of bacteria the results of which were reported to 
 the French Academy of Sciences, February ioth, 1896. 
 Their experiments have shown that cultures of bacteria are 
 affected more or less by the action of the constant or gal- 
 vanic current, the interrupted induced current of low ten- 
 sion and frequency, and also by the high tension, high fre- 
 quency currents. The action of the latter seems to be 
 most effective both in retarding the growth of pathogenic 
 bacteria and in weakening the virulence of their toxine 
 products. As has been elsewhere noted, the action of the 
 constant current upon culture media is attended by elec- 
 trolysis and is a difficult matter to determine, when this 
 current is used, just how much of the result is to be attri- 
 buted to the electric action directly and how much to the 
 action of the liberated ions. It is fair to presume that the 
 changes wrought by the high tension, high frequency cur- 
 rents are the result of the electric action solely since being 
 alternating currents but little electrolytic decomposition at- 
 tends them. 
 
 The experiments upon bacterial toxines by means of 
 high frequency, high tension currents and the subsequent 
 tests made with the solutions containing the toxines thus 
 acted upon, not only seem to show that the toxic power is 
 reduced, but also that the animal receiving such injections 
 is rendered immune, or its resisting power to such toxines 
 is greatly increased. From this the hope is entertained 
 that by means of the application of such currents it may, 
 eventually, be possible to so attenuate bacterial products 
 
Il8 LABORATORY MANUAL 
 
 in the organism of a patient as to render him immune to 
 the disease. 
 
 6th. The clinical results are also in evidence to prove 
 the modifying influence which electricity in this form ex- 
 erts upon physiological action, and while these are not as 
 yet very abundant they are already sufficient in amount 
 and importance to establish the value of this unique man- 
 ner of treatment, and are deserving of separate consider- 
 ation in the following article. 
 
 THERAPEUTICS OF HIGH POTENTIAL, HIGH FREQUENCY 
 CURRENTS. 
 
 Those who have been long familiar with the results 
 obtained from treatments by means of the static machine 
 cannot but be struck with the similarity of these with what 
 has recently been set forth by D'Arsonval, Apostoli and a 
 few others as the results of their experience in the thera- 
 peutic use of high frequency currents obtained through the 
 variously devised forms of apparatus that they have em- 
 ployed. Especially do the results on general nutrition ob- 
 tained by the spark and insulation methods of treatment 
 by the static machine closely correspond with those re- 
 ported as resulting from the inductive action of the large 
 solenoid. The assertion which is often made that "sug- 
 gestion " is accountable for much that is reported as re- 
 sulting from this as from other forms of electric treatment 
 falls to the ground in the face of the exact methods of an- 
 alysis that have been adopted in determining the effects of 
 these currents on patients in the public clinic and upon the 
 growth of infants in the Maternity hospital. But the field 
 is open and those who doubt may readily put all assertions 
 to the proof. 
 
 We perhaps cannot do better in our attempt to set 
 
OF ELECTROTHERAPEUTICS. 119 
 
 forth the present state of opinion as to the therapeutic 
 range and value of this peculiar electric modality than to 
 give as succinctly as possible the conclusions of Apostoli, 
 whose clinical experience in this field has been up to the 
 present time far more extensive than that of any other 
 practitioner. 
 
 They are as follows: 
 
 ist. The alternating currents of high tension exercise 
 a powerful action on every living organized body which is 
 submitted to their influence. 
 
 2nd. The best method of treatment by means of 
 these currents is to enclose the patient, without any con- 
 tact whatever, in a large solenoid traversed by the current. 
 The patient is thus completely insulated from the electric 
 source and the currents which circulate by "auto-conduc- 
 tion " in his organism have their origin, by induction, in 
 the tissues themselves. The body here plays the part of 
 a closed circuit. 
 
 3rd. The powerful influence on the vaso-rnotor sys- 
 tem claimed for these currents by d'Arsonval has been 
 verified, although the sensation immediately produced by 
 their passage is nil, and there is no impression made by 
 them on motor nerves or muscles. But an energetic ac- 
 tion on all nutritive exchanges may be noticed. This ac- 
 tion shows itself by an over-activity of organic combus- 
 tions and of nutrition, as has been shown by the analysis 
 of the respiratory and urinary excretions made by d'Arson- 
 val, Berlioz and others. 
 
 4th. The general therapeutic applications which fol- 
 low from this physiological action are confirmed in the 
 clinic. 
 
 At the time of this report (made at the London con- 
 gress in '95) Apostoli had in this manner treated more than 
 
120 LABORATORY MANUAL 
 
 one hundred patients, covering a period of a year and a 
 half, some in his office and some in his public clinic. The 
 greater number of them were much benefitted by this 
 method, which was used to the exclusion of all other treat- 
 ment or medication. 
 
 5th. These currents exercise, in the majority of 
 cases, a powerful and generally reparative action on dis- 
 eases caused by or attended with feeble nutrition, by ac- 
 celerating the organic changes and by increasing the activ- 
 ity of enfeebled or perverted combustion and elimination. 
 Diuresis becomes generally more satisfactory and excre- 
 tion is hastened. 
 
 6th. Generally in patients submitted to this influence 
 daily for about 12 minutes the following effects are noticed 
 about in the order named: 
 
 Return of sleep. 
 
 Increase in force and vital energy. 
 
 Return of good feeling, capacity to work, ease in 
 walking, increase of appetite. 
 
 Progressive and complete restoration of the general 
 health. 
 
 Often from the first sittings and even before the spe- 
 cial and local effects noticed as changes in the excretions, 
 etc., an amelioration of the general ill-state can be plainly 
 noted. 
 
 7th. The local troubles, pains or trophic distur- 
 bances, subside generally much more slowly under the 
 modifying influence of these currents than general nutri- 
 tive disorders. In many cases such local disorders require 
 the addition of local treatment. 
 
 8th. Of all the diseases, which up to the present seem 
 to yield to this treatment, rheumatism is most energetically 
 and effectively influenced. 
 
OF ELECTROTHERAPEUTICS. 121 
 
 9th. In some cases of diabetes the sugar has rapidly 
 disappeared from the urine, while in others it has not been 
 perceptibly diminished in spite of the manifest improve- 
 ment in the general state. This difference in result may 
 foe due to a lack of uniformity in technique or to different 
 pathological conditions. 
 
 To sum up in the words of d'Arsonval, electricity in 
 the form of high tension, high frequency currents is the 
 most powerful modifier of the intimate nutrition of the tis- 
 sues that we know. 
 
 It is a modifier which attacks life in its most intimate 
 manifestations and which touches the working of the liv- 
 ing cell itself. Its action extends even to the products of 
 the cell. As these currents can with impunity traverse the 
 organism of living man there is no temerity in saying that 
 by means of them an entirely new road for therapeutics is 
 opened up. 
 
 THE STATIC MACHINE. 
 
 We have in the beginning of the preceding article dis- 
 cussed the static machine as a source of high potential 
 high frequency currents. While, as there stated, it can- 
 not be depended upon to furnish currents oscillating in 
 character or of a uniform rate of oscillations, yet the elec- 
 tric modalities derived from the static machine have for 
 many years proved of valuable service in therapeutics. 
 
 Static, or frictional electricity is the form in which 
 this agent was first brought to the intelligent attention of 
 mankind and by which, therefore, it has been longest 
 known. The physiological effects of the static spark de- 
 rived from the crude apparatus of Von Guericke of Mag- 
 denburg, as early as the middle of the seventeenth century, 
 
122 LABORATORY MANUAL 
 
 was the means of directing the thought of physicians to 
 electricity as a therapeutic resource. But the machinery 
 for generating static or frictional electricity had to go 
 through many successive stages of experiment before it 
 furnished an instrument that could be relied on for thera- 
 peutic work. 
 
 The invention of influence machines by Holtz and by 
 Topler in 1865 met this want, and these with the later in- 
 vention of the Wimshurst machine now amply supply us 
 with instruments for dealing with such abnormal condi- 
 tions as can be successfully combated by means of static 
 electricity. 
 
 In the Holtz machine the original or primary charge 
 must be supplied to the machine, and this under suitable 
 conditions is multiplied by induction as the movable 
 plates .are rotated. When at rest, however, and when the 
 atmosphere is warm and humid, this machine readily loses 
 its charge and is at times recharged with much difficulty. 
 The Topler and Wimshurst machines are self exciting. 
 This feature in their action is obtained through augment- 
 ing the slight difference of potential that usually exists by 
 means of metal buttons, more or less in number, attached 
 at regular intervals to the surface of the revolving plates 
 and projecting so as to come in contact with metallic 
 brushes of tinsel or fine wire fixed on the ends of metal 
 rods. The friction caused by some of these brushes aug- 
 ments the initial charge while others of them serve the 
 purpose of discharging, by contact, the electricity accum- 
 ulateoVon that part of the plate which passes them. The 
 presence of these brushes, buttons and metal inductors on 
 the Topler and Wimshurst machines are somewhat of a 
 detriment to their insulation, and in this respect render 
 them inferior to the Holtz, of the same size, in the amount 
 
OF ELECTROTHERAPEUTICS. 
 
 123 
 
 of electric energy produced. But the conditions which 
 furnish the initial charge by friction in the former ma- 
 chines are constant while they are in motion, each revolu- 
 tion adding its increment of difference of potential from 
 this source, which renews the supply of electricity and 
 
 FIG. 46. HOLTZ MACHINE. 
 
 makes the generating capacity of these machines more 
 constant and reliable. 
 
 The manufacturers of the Holtz machine for medical 
 use have of late years furnished it with a small Wimshurst 
 for the purpose of exciting action in the Holtz when it 
 loses its charge, and the latest improved static machine of 
 the Holtz variety has a small Wimshurst included in the 
 case with it, so arranged that a charge from the small ma- 
 
-124 LABORATORY MANUAL 
 
 chine can be readily transferred to the plates of the larger 
 one. 
 
 The Wimshurst machine is especially reliable in crea- 
 ting a difference of potential and getting into action be- 
 cause its construction is such as to give a large amount of 
 friction between the metallic brushes on the stationary 
 plates and the carriers on the revolving plates. These 
 metal carriers or sectors are greater in number than on 
 the Topler machine and the arrangement which causes the 
 revolving plates to move in opposite directions favors a 
 rapid development of the charge. The mechanism of the 
 Wimshurst is not, however, well adapted to secure dur- 
 ability in a machine of large size, so that they are not so 
 well suited for developing quantity of electricity as either 
 the Holtz or Topler form. 
 
 All static machines for therapeutic work are now pro- 
 vided with Leyden jars as condensers, so as to increase the. 
 quantity of electricity in the resulting spark. When the 
 machine is in action the interior of one Leyden jar be- 
 comes charged positively, the other negatively, and the 
 outer coating of each jar by induction becomes charged 
 with an equal but opposite potential from that within. By 
 leading off conductors from the outer coatings of the Ley- 
 den jars, an induced current can be obtained and utilized 
 for therapeutic purposes. This current has been named 
 by its discoverer the "static induced current" and re- 
 sembles somewhat in nature the current derived from the 
 fine wire coil of a medical induction coil, as it is an alter- 
 nating, and interrupted current, but its potential is very 
 high, the E. M. F. being far in excess of that which any 
 medical induction coil can furnish. The frequency of in- 
 terruptions of this current depends upon the frequency 
 -with which discharges take place between the interior ar- 
 
OF THE 
 
 .UNIVERSITY 
 
 OF ELECTROTHERAPEUTICS. 125 
 
 matures of the Leyden jars at the spark gap which sepa- 
 rates the prime conductors, and as the width of this spark 
 gap is under the control of the operator the number of in- 
 terruptions and the strength of the "static induced" cur- 
 rent can be varied at will. 
 
 The resistance which the static machine is able to 
 overcome at the instant a spark crosses the air gap be- 
 tween the prime conductors shows us that we are here 
 dealing with electricity in a state of very high potential. 
 The E. M. F. of the direct currents which we have here- 
 tofore considered as adequate for electro-therapeutic work 
 is entirely inadequate to carry a current across the resist- 
 ance of the minutest air gap. And the most powerful 
 medical induction coil now in use gives an E. M. F. cap- 
 able of forcing a passage through but an infinitesimal film 
 of air resistance. But well constructed static machines of 
 fair size will readily develop an E. M. F. that will cause 
 the current to leap an air gap between the prime conduc- 
 tors of eight or ten inches (20 to 25 cm). The E. M. F. 
 required to overcome the resistance offered by such a 
 large interval of dry air is enormous. Although no care- 
 ful measurements of the E. M. F. of the static machine 
 are yet recorded, a rough estimate can be made from the 
 size of the air gap traversed by the current as shown by 
 the spark. 
 
 A spark i mm. in length would indicate an E. M. F. of 
 
 at least. . . . ............... . 2,000 volts; 
 
 One of i cm ............ ... 10,000 volts; 
 
 One of 10 cm .............. 100,000 volts; 
 
 One of 25 cm .............. 1,000,000 volts 
 
 approximately. 
 
 But while the voltage is extremely high the current 
 actually passing is exceedingly small, seldom more than- 
 the fraction of a milliampere. 
 
126 LABORATORY MANUAL 
 
 The spark is the result of a sudden breaking down of 
 the dielectric; that is, the air stratum between the prime 
 conductors. " The difference of potential has so far in- 
 creased by the working of the machine that the air stratum 
 no longer oilers sufficient resistance; it is in a state of 
 gradually increasing strain and finally gives way and a dis- 
 charge of electricity takes place equalizing the potential. 
 The spark is not itself electricity, but it is due to the heat 
 and light generated in the intervening particles of matter 
 as a consequence of the mechanical violence of the dis- 
 ruption. The discharge which causes the spark is ap- 
 parently unidirectional but in reality it is oscillatory in 
 character, the rapidity of the oscillations occurring with 
 marvelous frequency and gradually decreasing amplitude. " 
 The vibrations of one discharge may reach as high as a 
 hundred million or more per second. 
 
 The difference of potential which is created by the ac- 
 tion of the static machine seeks relief from the strain pro- 
 duced on the surrounding insulators or dielectrics in other 
 ways than through the sudden disruption which causes the 
 spark discharge. Foreign substances suspended in the 
 atmosphere as dust, or water vapor, become charged with 
 electricity of different potentials and are repelled from the 
 attracted to different parts of the apparatus, according to 
 the polarity. A stream of such particles may produce an 
 actual current in the air if escaping from some point or 
 edge where high degree of difference of potential is main- 
 tained. This is what constitutes the so-called "electric 
 breeze " and if it is accompanied by noise and light it is 
 termed a " brush discharge." 
 
 It is sometimes desirable to know, when using a static 
 machine in therapeutic work, which prime conductor has 
 positive and which negative potential. The position of 
 
OF ELECTROTHERAPEUTICS. 127 
 
 the prime conductor or Ley den jar will not serve to desig- 
 nate the potential since in the action of the machine the 
 potential may become reversed. The most satisfactory 
 method for determining which conductor is positive and 
 which is negative is to observe the machine while in action 
 in the dark, when the positive side can be recognized by 
 the tips of the collecting comb showing points of light 
 while upon the opposite or negative side the light appears 
 in brush-like form. 
 
 In order that a static machine may be kept up to its 
 highest efficiency care must be taken to preserve intact the 
 conditions essential to its action. Dust or moisture upon 
 the plates rapidly equalizes the difference in potential 
 created. Variations in the amount of moisture in the at- 
 mosphere affect the working of the machine. It is best, 
 therefore, to have the plates of the machine enclosed in a 
 case where they can be kept free from dust and where if 
 necessary the air can be subjected to artificial methods of 
 drying, either by means of a dish containing petroleum or 
 anhydrous calcium chloride placed within the case. All 
 unnecessary points and projections should be avoided in 
 the construction of the machine since they serve to dissi- 
 pate the electric energy produced. 
 
 The increase in the size and number of the plates in- 
 creases the quantity of electricity, but there is a point be- 
 yond which such increase possesses no additional thera- 
 peutic advantages. The prevalent opinion at present 
 among those experienced in the use of static electricity in 
 therapeutics is that a machine having eight plates, four re- 
 volving and four stationary, the revolving plates being 
 from 28 to 36 inches diameter, is capable of doing all that 
 is at present sought for from a machine of this kind. 
 
128 LABORATORY MANUAL 
 
 PHYSIOLOGICAL AND THERAPEUTIC ACTION OF STATIC ELEC- 
 TRICITY. 
 
 We have considered the structure and action of static 
 machines for therapeutic work and the physical properties 
 of the electric energy which they produce. It remains for 
 us to study the behavior of the human organism in health 
 and disease when subjected to electric conditions such as 
 the static machine and its accessories can furnish. 
 
 The extremely high electro-motive force of electricity 
 when generated by the static machine renders it prone to 
 break down the dielectric which surrounds all conductors 
 and other bodies charged with it and so escape. The di- 
 electrics or insulators that are employed in the operation 
 of the static electric machines which physicians use are the 
 glass plates of the machine itself, the glass of the Leyden 
 jars or condensers, the glass or hard rubber used for the 
 various supports of the conducting parts of the machine 
 as well as for the feet of the insulating stool, and lastly, 
 the air which surrounds all parts of the machine and the 
 objects in continuity with its conductors. In order that 
 a body may be subjected to a high degree of static charge 
 these various dielectrics must be capable of sustaining con- 
 siderable strain without giving out, that is, there must be 
 a sufficiently thick layer of air or glass or hard rubber 
 separating from surrounding objects the bodies and con- 
 ductors which the machine has brought to a positive po- 
 tential so as to prevent the charge from escaping to the 
 earth through some object which is in connection with it, 
 and may serve as a conductor. Particles of moisture or 
 dust in the atmosphere which surrounds the machine aid 
 in dissipating the charge which the machine creates, and 
 for this reason a dry atmosphere and one free from dust 
 
OF ELECTROTHERAPEUTICS. 129 
 
 is an essential if a static machine is to do its most suc- 
 cessful work. 
 
 The physical conditions created by means of static 
 machines that are employed in therapeutics may be enum- 
 erated as follows: 
 
 Static insulation, 
 
 The direct spark, 
 
 The indirect spark, 
 
 The friction spark, 
 
 The spray or breeze, 
 
 The needle spray, 
 
 The static induced current. 
 
 Static Insulation or Charge. A patient to be sub- 
 jected to this condition sits upon the insulated stool or 
 platform, which is attached to one or other, usually the 
 positive, pole of the machine by means of a conducting 
 chain or rod. When the machine is put in motion the 
 body of the patient, thus forming the terminal of the con- 
 ductor, is raised to such a potential as the machine is cap- 
 able of producing, and the patient becomes the storehouse 
 of a positive or negative charge, depending in amount 
 upon his or her electrical capacity. Just here there is 
 need of some careful study in the comparative effects of 
 positive and negative insulatioa. It is very generally 
 agreed among those who have employed this form of treat- 
 ment that it is followed by marked nutritional effects, yet 
 some claim that positive insulation is stimulating and bene- 
 ficial, and negative insulation is depressing and hurtful, 
 while others assert that there is no such noticeable differ- 
 ence in effects between them, but that either form of in- 
 sulation will prove tonic and invigorating. Only a care- 
 fully arranged series of tests faithfully carried out in both 
 the domain of physiology and therapeutics can satisfac- 
 
I 3 o 
 
 LABORATORY MANUAL 
 
 torily settle this mooted question. It is claimed for static 
 insulation, and as commonly employed this means positive 
 insulation, that it will elevate a subnormal temperature, or 
 lower a temperature abnormally high; that it will regulate 
 and increase the volume of the pulse; that it will decrease 
 the number but increase the depth of respirations; that to 
 a person nervously excited and sensitive, it imparts a seda- 
 tive effect and a sense of well being. The action appears 
 
 Fig. 47. 
 
 to be to improve nutrition and regulate disordered func- 
 tion, although the manner in which a static insulation or 
 bath operates to produce this effect has not yet been ex- 
 plained. 
 
 The Direct Spark (Fig. 47). In giving the direct 
 spark, the patient is placed upon the insulating platform 
 (F), which is connected by the chain or rod to either the 
 positive (B) or negative pole of the machine, and the first 
 effect upon the patient (P) is to produce a static charge of 
 either positive or negative potential, as the case may be. 
 Here again the positive charge for the patient is ordin- 
 
OF ELECTROTHERAPEUTICS. 13! 
 
 arily used and preferred. An electrode (H) terminating 
 in a metal or gilded ball about two inches in diameter is 
 attached to the other pole of the machine (B 1 ). When 
 this electrode is made to approach the body of the patient 
 at any point, the layer of air which surrounds the patient 
 and acts as a dielectric is thereby rendered thinner (G), 
 and less capable of sustaining the strain to which it is sub- 
 jected, and finally it is so thinned by the nearer approach 
 of the ball electrode that it gives way and the static charge 
 in the patient's body suddenly becomes transformed to 
 current electricity and escapes, leaping the air space in its 
 transit and causing a spark. 
 
 The physical phenomena here are the sudden dissipa- 
 tion of a static charge which had been maintained in the 
 charged body at a very high potential. The discharge is 
 often if not always oscillatory in character, the oscillations 
 numbering many thousands per second. The current by 
 reason of the extremely high resistance to be overcome at 
 several points in the circuit, is very small, usually but a 
 fraction of a milliampere. The human organism, which is 
 for us the point in the circuit of greatest interest, is sud- 
 denly subjected during a treatment of this nature to a high 
 electric potential, which it as suddenly, loses as often as the 
 ball electrode is brought sufficiently near to some part of 
 the body to cause sparking. As all parts of a charged 
 body are at a uniform potential a change must take place 
 throughout the entire organism when the potential is re- 
 duced to zero, as is the case when a spark crosses the air 
 gap, and if this discharge is not instantaneous in its decline 
 of potential but oscillatory, with gradually decreasing am- 
 plitude of oscillations, the organism must be subjected to 
 corresponding disturbances in its molecular arrangement 
 throughout. The tissues of the human body are not uni- 
 
132 LABORATORY MANUAL 
 
 form in conductive capacity, consequently the density of 
 the charge is not uniform throughout the entire organism. 
 Both during charge and discharge therefore, the human 
 body must be supposed to act quite differently from a mass 
 of metal of equal size and form under similar electric con- 
 ditions. Certain of the tissues conduct readily while others 
 possess the characters of dielectrics. There would, there- 
 fore, be innumerable spots of strain and slip in close re- 
 lation which must be taken into account when we attempt 
 to analyze the eifects produced during a static treatment. 
 But whatever may be the fact as to the spark discharge 
 causing molecular excitation of the entire organism, a ser- 
 ies of phenomena capable of ocular demonstration always 
 occurs at that part of the body where the discharge takes 
 place. There is a sudden blanching of the skin, due to 
 vaso-motor constriction over a circular spot greater or less 
 in diameter, according to the strength of the discharge; 
 this is soon followed by a vaso-motor dilatation and the 
 spot is correspondingly reddened, a condition which re- 
 mains for a considerable length of time after the treat- 
 ment. The muscles underlying the point from which the 
 discharge takes place are caused to contract and sensa- 
 tions of a variable nature, referred to the same spot, are 
 prominent accompaniments. These sensations are an im- 
 portant element in the treatments for upon their nature of- 
 ten depends the good or bad effect which the patient ex- 
 periences. The direct spark from small machines is much 
 more likely to be stinging, pricking and irritating than 
 from large machines, and it is claimed that grounding the 
 machine has the effect to render the spark much less dis- 
 agreeable than when the circuit is confined to the machine, 
 the conductors and the patient, as is the case when using 
 the direct spark. The static spark is of great value in 
 
OF ELECTROTHERAPEUTICS. 133 
 
 arousing to more active nutrition any organ of the body 
 that is subjected to this treatment. The skin, the vascular 
 tissues, muscles and nerves are stimulated by it. Its effects 
 are more generally distributed throughout the body than is 
 the case with the direct or induced current applications, 
 so that it is well suited for correction of systemic disorders, 
 such as rheumatism, gout, neurasthenia, spinal irritation 
 and general sluggishness in nutrition from whatever cause. 
 Unmistakable evidence is given of its power to quicken 
 nutritive processes by the way in which the sweat and 
 sebaceous glands are set to work by it, and the improved 
 bodily comfort that follows such applications, is due in a 
 great measure, no doubt, to the more perfect elimination 
 of effete matters from the body. 
 
 It is sometimes difficult to give the spark treatment to 
 special localities of the body by means of the ordinary ball 
 electrode for the reason that the current which causes the 
 spark invariably seeks the line of least resistance. A di- 
 rective electrode, such as the Morton electrode is of much 
 service in getting exact local eifects, and by means of it the 
 spark can be drawn from accessible surfaces within the 
 cavities of the body when this is thought desirable. 
 
 The Indirect Spark (Fig. 48.) In order to get the 
 indirect spark the machine must be "grounded." This is 
 done by putting the negative prime conductor or pole of 
 the machine in communication with the earth by means of 
 a conductor running from it to a convenient gas pipe or 
 water-pipe. The electrode used for the purpose of draw- 
 ing sparks should also be grounded. This has the effect 
 of increasing the quantity of electricity which the machine 
 generates and improving the constancy of its action. The 
 spark is likely to have more volume and is cleaner, with 
 less irritating properties. It is more satisfactory, there- 
 
134 
 
 LABORATORY MANUAL 
 
 fore, when using the spark treatment to have the machine 
 grounded. A sputtering series of sparks is very disagree- 
 able to most patients and irritates the sensory nerves and 
 should always be avoided except when this effect is sought 
 for, as in the case when counter-irritation or skin excita- 
 tion is desired. It insures a clean, full, individual spark 
 
 I 
 
 Fig. 46. 
 
 to have the machine well grounded and then make the ball 
 electrode approach the part of the charged body suddenly 
 to within the proper distance and as suddenly withdraw it. 
 
 The purpose and manner of the treatment with the in- 
 direct spark is the same as that with the direct spark, but 
 the effect differs because of the physical and physiological 
 differences which they possess. 
 
 The Friction Spark. This is used mainly for ex- 
 citation of the skin or the superficial blood vessels and is 
 a convenient method for applying mild counter-irritation. 
 The patient is insulated as with the spark treatment. A 
 roller electrode is provided for this application but is not 
 necessary since the large ball electrode will serve the same. 
 
OF ELECTROTHERAPEUTICS. 135 
 
 purpose. The only physical difference between this and 
 the direct or indirect spark is that the dielectric is thinned 
 down to a layer which is represented by the thickness of 
 the patient's clothing. The roller or ball is passed over 
 the spot treated directly in contact with the clothing, con- 
 sequently the charge escapes at more frequent intervals 
 and with smaller sparks but with a prickling, biting or 
 stinging effect upon the sensory nerves of the skin which is 
 decidedly exciting to their function and the reflex effect 
 upon the nutrition of the skin is marked. 
 
 This form of treatment is of special service in correc- 
 ting chronic malnutrition of the skin as in eczema and sen- 
 sory paresis. 
 
 The Spray or Breeze. Again the patient is insu- 
 lated as before but the charge is withdrawn, not suddenly, 
 as in the forms of treatment thus far mentioned; but slowly 
 and in infinitesimal quantity by holding a pointed elec- 
 trode at such distance from the part of the body to be 
 treated that the discharge is not disruptive but is conveyed 
 away by the particles of air forming the dielectric layer, 
 each becoming charged with its load and seeking the oppo- 
 site potential. This creates a current in the atmosphere 
 surrounding the part of the patient's body under treat- 
 ment. This motion together with the gentle stimulating 
 effect caused by the slight loss of potential in the surface 
 which each instant takes .place by the process of convec- 
 tion that is going on, constitutes the treatment. 
 
 The pointed electrode may be moved about over the 
 patient's body. Or, by fixing it upon a stand, it can be so 
 placed that the effect may be maintained for any desired 
 length of time upon a particular part. A circle of points 
 fixed at a suitable distance above the patient serves to dis- 
 tribute the ''spray " or <( breeze" uniformly over the head, 
 
136 LABORATORY MANUAL 
 
 The static spray or breeze is peculiarly soothing and 
 resting in its effects. By means of it a condition of ner- 
 vous excitement and restlessness can be almost immedia- 
 tely allayed. Severe headaches of a nervous type are of- 
 ten quickly relieved and insomnia is frequently overcome. 
 
 The Needle Spray. When only a part of the pa- 
 tient's body is brought in the direct line of charge, and so 
 is raised to a higher potential, as would be the case if the 
 conducting chain is held in the patient's hand instead of 
 being placed on the insulating stool, and the pointed elec- 
 trode is then brought near enough to the part to be treated 
 to allow of minute disruptive drops of potential instead of 
 the discharge by convection, the effect upon the part under 
 treatment is much as if it was being pricked by innumer- 
 able fine needles. This is decidedly stimulating, though 
 at the same time irritating, and is in all respects of the 
 same nature and used for the same purpose as the friction 
 spark above described. 
 
 The Static Induced Current. The static induced 
 current is that current which results from a return to zero 
 of the difference of potential that is created between the 
 outer coatings of the Leyden jars or condensers attached 
 to the prime conductors of the machine (Fig. 49). At 
 each instant that a discharge takes place between the prime 
 conductors, the potential difference which existed in the 
 interior of the Leyden jars is equalized and a correspond- 
 ing discharge takes place between the exterior surface of 
 these jars and this latter current can be utilized for thera- 
 peutic applications without the disagreeable accompani- 
 ment of sparks. The electrode for applying this current 
 can also be placed in contact with the body and the var- 
 ious tissues and organs be brought under its influence with 
 more precision than is possible in the use of the spark or 
 
OF ELECTROTHERAPEUTICS. 
 
 137 
 
 spray. All modern static machines designed for therapeu- 
 tic work are furnished with connections that permit the use 
 of the static induced current. For the regulation of this 
 current it is only necessary to regulate the discharge be- 
 tween the prime conductors of the machine. A small 
 spark gap permitting frequent minute discharges will be at- 
 tended by a similar frequency and feebleness in the static 
 induced impulses. A wider separation of the prime con- 
 ductors will result in heavier discharges at longer intervals. 
 The strength and frequency of the impulses of the static 
 induced current is thus readily controlled. The nature of 
 
 ' 
 
 Fig. 49. 
 
 this induced current is similar in potential to that of the 
 inducing current. The milliamperage depends upon the 
 resistance offered in the circuit. It is in all probability, 
 at times at least, oscillatory in character, although this re- 
 mains to be determined with certainty. As to the physio- 
 logical effects and the therapeutic applications of the sta- 
 tic induced current we quote the words of Dr. Morton, 
 whose rich experience in the use of this current gives to his 
 Conclusion? the weight of authority. 
 
138 LABORATORY MANUAL 
 
 " Applied to a motor point, the static induced current 
 produces most vivid and persistent muscular contraction 
 with a minimum of pain; applied farther back on the trunk 
 of a motor nerve it throws large groups of muscles into 
 contraction. The contraction is peculiarly painless as 
 compared with that of faradic coils, and the influence is 
 remarkably effusive. Accompanying a contraction of a 
 large group of muscles is a peculiar sensation of lightness 
 and buoyancy of the member. The painlessness, diffusive- 
 ness, and buoyancy may all be experienced by holding the 
 two electrodes in the hands, and taking a current as strong 
 as possible. Most people will readily submit to flexions 
 successively at the wrists, elbows, and even to the shoul- 
 ders before insisting upon taking no more. The arms dur- 
 ing the passage of the current feel as if made of cork, and 
 this feeling of lightness persists for some time. It is the 
 same feeling, doubtless, though here exaggerated, as is 
 commonly referred to as the refreshing effect of general 
 electrization. The quality of the current is such, that while 
 energetically exciting the motor function of the nerve fila- 
 ments, it fails to excite or may even annul, to an extent, 
 the sensation of muscular pain. Its penetrating, diffusive, 
 painless effect, with strong muscular contractions, adapt 
 it admirably to general application over the entire body as 
 an electric in place of an ordinary massage. 
 
 " It is, of course, applicable to every form of muscu- 
 cular paralysis, for there is no practical stimulus to nerve 
 and muscle except the electric, and none more energetic 
 than this form of it 
 
 " Its effects upon the Hallerian irritability of the mus- 
 cular tissue necessarily includes an effect upon the local 
 circulation of a part and upon the lymphatics, and to this 
 may doubtless be referred many clinical results of relief 
 
OF ELECTROTHERAPEUTICS. 139 
 
 as in lumbago and all forms of muscular rheumatism, sub- 
 acute and chronic rheumatic affections of the joints, ovar- 
 ian or pelvic pain, sciatica or other neuralgias. 
 
 "The second prominent characteristic of this current 
 is its power of relieving pain. Leaving out of sight the 
 part, be it more or less, played by circulatory changes re- 
 ferred to, in this respect there seems to exist a specific 
 analgesic quality in the current. The cotton feeling in 
 the hands and subjective sense of buoyancy in the arms is 
 in itself an evidence of this. But the effect upon pelvic 
 pain, upon ovaritis, upon neuralgias, pleuritic 'stitches,' 
 tonsillitis, and many other pain affections is still better 
 evidence. In sciatica, for instance, the sensation of pain 
 is frequently quickly relieved and a cure obtained, though 
 I think in this case the cause is two-fold that is to say, 
 due to both the circulatory and the analgesic effect. The 
 same I believe to be true in the pelvic and ovarian pains. 
 
 " The results in such cases, in my opinion, are far 
 superior to anything obtainable by a faradic or a galvanic 
 application. An ordinary faradic current will increase the 
 pain; the galvanic will very often relieve it. But we have 
 in the static induced current no comparison to the electro- 
 tonic and polar effects, or in general the electrolytic effects 
 of the direct or galvanic current. Therefore, when the 
 static induced current has failed to act favorably, we should 
 try the galvanic, and vice versa. As no observations on 
 the purely analgesic effects of this current have hitherto 
 been made, I must leave others to test the question for 
 themselves." 
 
 It will be seen from this brief review of the methods 
 of practical application of the effects obtained by means 
 of the static machine that it is capable of doing a variety 
 of work in therapeutics which no other form of electrical 
 
140 LABORATORY MANUAL 
 
 apparatus can accomplish; but the good results obtainable 
 can only follow when the action of the machine is fully 
 understood by the operator and the case to be treated is 
 one adapted to the form of treatment employed. 
 
 EXPERIMENT 96. Turn the crank of the static ma- 
 chine until the sparks are passing between the prime con- 
 ductors. Notice the difference in this discharge when the 
 Leyden jars are attached and when they are not. Also 
 notice the effect of connecting and disconnecting the 
 metal coatings on the outer surface of the Leyden jars. 
 What is the explanation of these differences? 
 
 EXPERIMENT 97. Determine which prime conductor 
 is charged positively and which negatively. Observe 
 what effect, if any, the discharge has upon litmus paper. 
 Does it electrolize? Does it move the needle of the 
 galvanometer? 
 
 EXPERIMENT 98. Positive Insulation. Let some 
 member of the class take the place of a patient and sit 
 upon a stool placed upon the insulated platform. Connect 
 the subject, by means of a well-insulated conducting cord, 
 with that prime conductor of the static machine which is 
 charged positively when the machine is in action. 
 
 Separate the prime conductors of the machine so that 
 no discharge takes place across the space between them. 
 After the machine has been in action for a few moments 
 notice that an electric discharge will readily take place at 
 any point on the subject's body which is approached by a 
 conductor, as, for instance, the finger of the operator. 
 This shows that the subject's body has received a static 
 charge of positive potential. 
 
 EXPERIMENT 99. Direct Spark. Separate the 
 prime conductors and unite by a conducting cord the outer 
 surfaces of the Leyden jars. Connect the subject on the 
 
OF ELECTROTHERAPEUTICS. i^l 
 
 the insulated platform with the prime conductor charged 
 positively. 
 
 Let someone take the place of operator and connect 
 a large ball electrode to the negatively charged prime 
 conductor by means of a suitable cord. Then holding 
 the ball electrode by the insulating handle and putting the 
 machine in action let him bring the ball electrode near to 
 some part of the subject's body, such as the shoulder or 
 back, until a spark discharge takes place. 
 
 EXPERIMENT 100. Indirect Spark. With the 
 prime conductors separated and the outer surfaces of the 
 Leyden jars connected have the subject connected with 
 the positively charged prime conductor, as in the pre- 
 ceding experiment. Join the negatively charged prime 
 conductor with some near at hand gas-pipe or water-pipe 
 which has a ground connection. This "grounds" the 
 machine. To the same or another water or gas-pipe the 
 ball electrode is then connected and brought near to some 
 part of the subject's body as before until a spark discharge 
 takes place. 
 
 EXPERIMENT 101. Friction Spark. Let the ar- 
 rangement for the subject and the connections be the same 
 as in giving the direct or indirect spark. The operator 
 should then place the ball electrode upon some not very 
 sensitive part of the subject's body, such as the back or 
 limbs, and as closely in contact with the skin as the cloth- 
 ing will permit. Then with the machine in action the ball 
 electrode should be moved about over the parts of the 
 body to be treated and kept in contact with the clothing. 
 The charge is discharged by means of fine and frequent 
 sparks giving a decidedly counter irritant effect. 
 
 EXPERIMENT 102. The Static Breeze. With sub- 
 ject and connections, as in the preceding experiment, sub- 
 
142 LABORATORY MANUAL 
 
 stitute for the ball electrode a metal circlet with points 
 and suspend it a few inches above the subject's head. 
 
 Or, instead of a ball electrode, let the operator use 
 one terminating in a sharp point and move it about near 
 the part of the body of the subject that is to be treated. 
 How does this method of discharge differ physically from 
 that which causes a spark? 
 
 EXPERIMENT 103. Static Induced Current. To 
 the outer metal coatings of the Leyden jars connect 
 electrodes such as are used to give a treatment with the 
 induction coil current. Separate the prime conductors so 
 as to leave, at first, not more than a quarter inch gap be- 
 tween them. With the subject on the insulated stool place 
 the electrodes on the part of the body that you wish to 
 treat and set the machine in motion. Observe that the 
 strength of this current is determined by the length of the 
 spark gap which you maintain between the prime con- 
 ductors, which can be varied at will. 
 
 DIAGNOSIS BY RONTGEN, OR X-RAYS. 
 
 Any advance or improvements in methods of diag- 
 nosis is a substantial gain. Electricity had already done 
 much to render the diagnosis of disorders of the muscular 
 and nervous system and pelvic organs more exact, but re- 
 cent discoveries of the effect of the action of high tension 
 currents of electricity in vacuum tubes have greatly 
 enlarged its field of usefulness in diagnosis and both sur- 
 geon and physician are now able to add the sense of 
 sight to that of touch and hearing, in determining the 
 state and condition of the deep seated tissues of the body. 
 
 No one can as yet set any limit to the practical appli- 
 
OF ELECTROTHERAPEUTICS. 143 
 
 cations that will be made of Rftntgen rays in revealing what 
 to human vision is otherwise unseen. Already the mem- 
 bers of the medical profession have found from them such 
 help as to give promise that the date of Rontgen's discov- 
 ery will mark a period of advance in medical science as 
 important as the discoveries of Jenner or of Lister. 
 Already enough has been done to show that not only all 
 parts of the bony skeleton, with its defects can be por- 
 trayed in minute and exact detail, but the structure of the 
 softer tissues and organs, also, their normal outlines and 
 density, together with their departure from the normal 
 have to some extent been revealed to sight. 
 
 So far as is at present known the creation of these 
 peculiar rays by means of which the human eye is enabled 
 to see, pictured upon fluorescent screen or photographic 
 plate, the things of the body hidden beneath the surface, 
 is dependent upon the action of the electric current. This 
 gives rise to another demand upon the medical profession 
 to become practically familiar with the phenomena of 
 electric physics. The essentials for skiagraphic diagnosis 
 are: 
 
 Some kind of apparatus for generating a suitable elec- 
 tric current. 
 
 A Crookes tube. 
 
 A fluorescent screen or photographic plate. 
 
 CURRENT GENERATORS FOR RONTGEN RAYS. 
 
 There are three forms of electric apparatus which 
 have so far been used to generate currents suitable for pro- 
 ducing X-rays; 
 
 The ordinary induction coil; 
 
 The static or influence machine, and 
 
 The disruptive discharge coil. 
 
144 LABORATORY MANUAL 
 
 By the ordinary induction coil we mean one of the 
 ordinary form of construction, such as the Ruhmkorif coil 
 pattern, with a vibrating, or what is better, a rotating com- 
 mutator break. This form of electric generator has been 
 used more than any other by those who have experimented 
 with X-rays. The interest in this subject has stimulated 
 manufacturers to produce excellent instruments of this kind 
 until now very reliable Ruhmkorff coils, capable of giving 
 a six, eight or ten-inch spark between the secondary termi- 
 nals can be obtained. 
 
 It may be safely said that a high potential capacity in 
 the electric generator is the first essential to successful 
 X-ray work. So that if a Ruhmkorff coil is used its ca- 
 pacity should be considerable. One giving a three or four- 
 inch spark will serve for generating rays capable of mak- 
 ing shadow pictures of the extremity of the body, but 
 stronger action is required if the thorax, abdomen or 
 pelvis needs to be traversed by the rays. It is best to take 
 the initial current used to excite the coil from some con- 
 stant and uniform source of supply as storage batteries or 
 a direct current dynamo circuit such as is used in some 
 places for producing incandescent light. The intensity 
 of current needed depends very much upon the condition 
 of the tube that is used, but with a coil of large capacity 
 the action of the coil can be varied to suit the require- 
 ment of the tube. 
 
 A Static Machine, when run by a motor, and con- 
 stant in action is a good Rontgen ray exciter because of 
 the high potential it creates. It is the current resulting 
 from induction in the outer coating of the Leyden jars 
 attached to the prime conductors of the static machine 
 that is used the so-called "static induced" current. 
 Rather more care is needed to preserve the tubes from 
 
OF ELECTROTHERAPEUTICS. 145 
 
 perforation when using the static machine as a generator 
 than when using the coil since there is liable to be consid- 
 erable variation in the strength and volume of the sparks 
 between the prime conductors even with the same spark- 
 gap interval. A four or six plate machine with plates of 
 from twenty- four to thirty-six inches in diameter, if its ac- 
 tion is good, will serve very well as an X-ray producer. 
 
 But if we are to depend upon ROritgen rays and skia- 
 graphs or flouroscopes to aid us in diagnosis there must be 
 no limit to the quantity or penetrating power of the needed 
 rays. Both the Ruhmkorff coil and the static machine 
 have their limitations. In the former they are due to its 
 mechanical construction and in the latter the expense 
 and lack of constancy in action. Some form of cheaply 
 constructed disruptive discharge coil of the Tesla or 
 Thomson type producing high-tension, high-frequency 
 currents, and which could be attached to a dynamo circuit,, 
 such as is now so universally employed for illuminating 
 purposes, gives promise of meeting the requirements in 
 furnishing a convenient and reliable source of electric, 
 energy of any potential desired for exciting vacuum tubes. 
 
 Under these conditions torrents of high fre- 
 quency discharges pass between the discharging knobs, 
 of the induction coil which are separated to the dis- 
 tance of, perhaps, 5 millimeters, the frequency being 
 determined by the capacity and inductance of the Leyden 
 jar circuit including the Tesla primary. These high-fre- 
 quency discharges induce in their turn high-frequency and 
 high-potential discharges in the tube. In such cases both 
 electrodes of the tube are alternately cathodes, and the 
 glass wall opposite to each electrode becomes fluorescent 
 and therefore the source of Rontgen rays. 
 
 10 
 
146 LABORATORY MANUAL 
 
 VACUUM TUBES. 
 
 Perhaps no part of the apparatus required, in the 
 present stage of our knowledge, for the production of 
 Rontgen rays has received so much attention as the vacuum 
 tubes in which the antecedent cathode rays are generated. 
 A volume could be written upon this subject and what 
 can be said in a few paragraphs will perhaps to some 
 appear very meagre. We must refer those who wish to 
 investigate the subject more deeply to the pages of the 
 electrical and scientific journals or to some special work 
 on the subject. 
 
 Success in making skiagraphs depends very largely on 
 a familiarity on the part of the operator with the action of 
 the tube and the changes that may take place in it while 
 undergoing bombardment. 
 
 Shape of the Tube. It is now well known that the 
 best tubes for producing efficient X-rays are those so con- 
 structed as to concentrate or focus the cathode rays either 
 on a reflecting surface within the tube or a convenient 
 spot on the wall of the tube itself. 
 
 The source of the X-rays is the point against which 
 the cathode rays are first projected. Whether this be the 
 wall of the tube or some other surface within the tube. 
 The cathode rays can be concentrated upon this point 
 both by the shape of the cathode electrode and the shape 
 of the vacuum. It is well, therefore, to give such con- 
 vexity to the shape of the cathode as will focus the cath- 
 ode rays at a desired point. Cathode terminals made of 
 aluminum seem to work best, and since the material of 
 the cathode is gradually worn away by the action, the size 
 and thickness should be considerable. If it is designed 
 to have the cathode rays first strike the wall of the tube 
 and there create X-rays, the anode terminal may be of 
 
OF ELECTROTHERAPEUTICS. 147 
 
 aluminum also and terminate in a point or in a ring; the 
 latter is better since it does not heat so quickly. But if 
 the anode terminal is to be used as the point of contact or 
 impingement of the cathode rays and so generate the 
 X-rays, then it is best to have it made of a sheet of plat- 
 inum and set at such angle as will direct the X-rays to 
 emerge at the spot on the tube where the glass has been 
 purposely blown thin. When the X-rays are once created 
 their escape from the tube should be facilitated as much 
 as possible, and this is best done by having the glass at 
 the point of their exit blown as thin as is consistent with 
 the safety of the tube. 
 
 A long narrow tube, therefore, with comparatively 
 thick walls, but thinned opposite the point of impact or 
 emergence of the X-rays appears to be the most efficient 
 shape. The best work has been obtained from this, or 
 from some form of " focus" tube. The length of the 
 tube should be selected to correspond with the potential 
 used. The higher the potential the longer the tube will 
 need to be, and if a very high potential, as from a disrup- 
 tive discharge coil, is used, it may be found necessary to 
 limit the electro-static action created about the tube by 
 immersing it in oil. 
 
 The Vacuum. More seems to depend upon the elec- 
 tric potential employed than the degree of rarefaction 
 within the tube, for even with comparatively low vacua 
 X-rays are generated with high potentials. The vacuum 
 increases very much during the action of the tube. This 
 is thought by some due to an actual propulsion of mole- 
 cules through the walls of the tube, while others believe 
 the walls absorb and retain the gaseous particles. When 
 from action the vacuum grows so high as to impede the 
 discharge through the tube, it can be readily reduced by 
 
I 4 8 LABORATORY MANUAL 
 
 gently heating the tube with the flame of a spirit lamp or 
 Bunsen burner. The heating appears to set free the gas- 
 eous particles from the walls of the tube. The degree of 
 vacuum suitable for generating X-rays bears direct rela- 
 tionship to the electric excitation and the best action of 
 any tube can only be determined by experience with it. 
 
 Action in the Vacuum Tube. This has been most 
 graphically and accurately portrayed by Tesla. "When 
 the Crookes phenomena show themselves most promi- 
 nently there is a reddish streamer issuing from the elec- 
 trode, which in the beginning covers the latter almost 
 entirely. Up to this point the bulb practically does not 
 affect the sensitive plate although the glass is very hot at 
 the point of impact. Gradually the reddish streamer dis- 
 appears, and just before it ceases to be visible the bulb 
 begins to show better action, but still the effect upon the 
 plate (or screen), is very weak. Presently a white or 
 even bluish stream is observed, and after some time the 
 glass on the bottom of the bulb gets a glossy appearance. 
 The heat is still more intense and the phosphorescence 
 through the entire bulb is extremely brilliant. One should 
 think that such a bulb must be effective, but appearances 
 are often deceitful, and the beautiful bulb still does not 
 work. Even when the white or bluish stream ceases and 
 the glass on the bottom is so hot as to be nearly melting, 
 the effect on the plate is very weak. But at this stage 
 there appears suddenly at the bottom of the tube a star- 
 shaped changing design, as if the electrode would throw 
 off drops of liquid. From this moment on the power of 
 the bulb is increased ten-fold, and at this stage it must 
 always.be kept to give the best results." 
 
OF ELECTROTHERAPEUTICS. 149 
 
 FLUORESCENT SCREENS AND SENSITIZED PLATES. 
 
 The quality which certain substances possess of fluor- 
 escing when exposed to these invisible rays was not only 
 the road to their discovery, but serves as a very ready 
 means for detecting the presence and quantity of the rays. 
 Rontgen made use of a fluorescing screen made of platino- 
 cyanide of barium. Salvioni had none of this material at 
 hand when he wished to construct what he has termed his 
 cryptoscope, but tried calcium sulphide, which he found 
 worked very well. He spread it on to the card-board end 
 of a tube by means of fish-glue, while in the end of the 
 tube near the eye he placed a lense which made the card- 
 board phosphorescing under the influence of the X-rays, 
 more distinctly visible. Following in this line of experi- 
 ment Edison not only discovered a long series of substances 
 which fluoresce under the influence of X-rays, but he found 
 among them tungstate of calcium to be by far the most 
 efficient, and from these researches fluoroscopes were de- 
 veloped which now are indispensable to skiagraphy. A 
 thin flim of fluorescing material placed in contact with the 
 photographic plate greatly reduces the time of exposure for 
 making a negative. 
 
 The fluoroscope does not take the place of the sensi- 
 tized plate in diagnosis, for the shadows cast upon it are 
 not so sharp and distinct as those formed on the photo- 
 graphic film, and it leaves no permanent record. Yet it 
 serves as a rough and ready means for examination and is 
 most helpful in determining the action of the tube and fix- 
 ing upon the best time for an exposure of the plate. 
 
 Serious injury to the skin and sometimes to deeper 
 tissues is caused by too prolonged or too intense action 
 upon them of some influence emanating from the excited 
 Crookes tube. While it is not yet positively known what 
 
150 LABORATORY MANUAL 
 
 causes this injury, it is in all probability due to a bombard- 
 ment of the tissues by microscopic particles of metal or 
 glass carried off from the metal of the electrodes or the 
 glass of the tube and driven into the tissues by the action 
 of the static charge which they possess. It is found that 
 if a thin sheet of aluminum or wire gauze of the same 
 metal is placed between the Crookes tube and the part of 
 the body being skiagraphed, and is then grounded it will 
 effectually prevent any injury to the tissues. As such a 
 grounded screen would serve to draw the static charge as 
 well as to intercept the particles, the result of its action 
 well accords with the theory above advanced as to the cause 
 of such injury. 
 
 EXPERIMENT 104. Excite the Crookes tube by means 
 of the static machine or the induction coil, and observe by 
 means of the fluoroscope the relation between the naked- 
 eye appearance of the tube and the illumination of the 
 fluoroscope screen. Observe the denning power of the rays 
 on the bones and joints of your hand and wrist, placing 
 the hand undergoing examination directly in contact with 
 the outer surface of the fluoroscope. 
 
 EXPERIMENT 105. Use a six by eight sensitized plate 
 or film enclosed in a thick layer of dark paper or in a plate- 
 holder, and placing some part of your hand or arm in con- 
 tact with it at a distance of eight or ten inches from the 
 Crookes tube, excite the tube for four or five minutes in 
 such manner as you have found generates X-rays most 
 abundantly. Then carefully develop the plate or film and 
 study the result. Be careful not to expose the sensitized 
 plate to the action of the X-rays before you are ready to 
 make the picture or after it is taken. 
 
RELATION OF MAGNETISM TO LIVING OR- 
 GANISM. 
 
 The intimate relationship existing between electricity 
 and magnetism, the inseparableness of their phenomena, 
 make it more than probable that when electric energy is 
 operating magnetic stress must be credited with a portion 
 of the work accomplished, and vice versa. Whenever a 
 current of electricity traverses an animal body in any 
 direction the magnetic field resulting from the passage of 
 the current and surrounding its path must disturb in some 
 manner the molecular and atomic activities that are going 
 on within its range in the tissues and fluids through which 
 the current of electricity passes. The amount of this dis- 
 turbance will depend upon the strength and character of 
 the magnetic stress which makes up this field or, in other 
 words, upon the strength and nature of the electric cur- 
 rent. 
 
 A constant uni-directional current will create a mag- 
 netic field of constant polarity and of uniform tension. 
 A uni-directional current, but of varying strength, will cre- 
 ate a corresponding magnetic field, pulsating or varying in 
 intensity. While an alternating current will be attended 
 by a magnetic field alternating in polarity with a frequency 
 corresponding to the alternations of the electric current 
 and of an intensity varying in degree with the strength of 
 that current. 
 
 We have found that the most noticeable physiological 
 response to an electric current obtained from living ani- 
 mals is that resulting from sudden and wide differences of 
 
152 LABORATORY MANUAL 
 
 potential. We would naturally expect, therefore, that a 
 magnetic field with rapidly reversing polarity and sudden 
 variations in its intensity would produce more noticeable 
 results in a living organism than would a more uniform or 
 constant field. 
 
 Careful scientific observation and record of the rela- 
 tion of magnetic stress to physiological action, either in 
 vegetable or -animal structure, separate from the effects 
 produced by the passage of the current of electricity itself 
 has been attempted by few. What has been done so far 
 has led to contradictory conclusions. Experiments have 
 for sometime been carried on in this laboratory with the 
 view of gaining some exact knowledge of the amount of 
 change in ordinary life processes that can be brought 
 about by the modifying influences of various forms of 
 magnetic stress. 
 
 These experiments were commenced more than two 
 years ago in this laboratory upon man and growing ani- 
 mals by subjecting them for a considerable length of time 
 to the influence of alternating magnetic fields. 
 
 This was done by constructing a solenoid three feet 
 in diameter, of number 10 underwriters wire, and with a 
 sufficient number of turns so that a current strength of 
 five amperes produced an average of sixty-five C.G.S. 
 lines for each square inch of space in a plane cross-sect- 
 ing the space within the coil. Both for convenience and 
 to determine the value of what we already have at hand, I 
 used the current from a Thompson & Houston alternat- 
 ing dynamo employed for electric lighting, to excite the 
 coil, or solenoid. This dynamo makes 124 cycles per 
 second or 248 alternations. So that the magnetic field or 
 stress in the space enclosed by the coil changed its polar- 
 ity with this frequency. Whatever occupied this space 
 
OF ELECTROTHERAPEUTICS. 153 
 
 therefore was subjected to this rapidly reversing and vary- 
 ing magnetic stress. 
 
 The first series of experiments was made with the 
 view of determining the influence of this magnetic field on 
 the metabolism of tissue as determined by the output of 
 urea. Three subjects were chosen. Two of them healthy 
 young men, students of medicine, and the other a man of 
 thirty-eight years of age who had for two years been suf- 
 fering from paralysis agitans, but who, aside from this 
 nervous affection, was in fair health. The diet was regu- 
 lated in amount and variety in each case for a week pre- 
 vious to subjecting them to the magnetic action, and a 
 daily estimate was made of the amount of urea excreted. 
 Then for a week's time without change of diet or man- 
 ner in living in any other respect each one of the three 
 subjects was placed within the solenoid, comfortably out- 
 stretched upon a platform, and remained there for two 
 hours each day, their bodies pervaded by the alternating 
 magnetic stress of the average strength above mentioned. 
 During this week also a daily estimate of the quantity of 
 urea was made, and it was found that in all three cases 
 there was a daily increase of about 10 per cent, in the 
 amount eliminated during the period in which the subject 
 was in the magnetic field. No other effects were noticed 
 that could be detected by this method of observation. 
 There was no apparent change in the depth or frequency of 
 respirations nor in the strength nor frequency of the pulse 
 or arterial tension; though it is possible that had more 
 delicate or exact methods of testing for such changes than 
 the unaided eye and touch been employed, some differ- 
 ence in these functions would have been observed. The 
 subjects were conscious of no change in sensation or 
 motive power except that the patient with paralysis agitans 
 
LABORATORY MANUAL 
 
 claimed that the period spent within the coil had a sooth- 
 ing and quieting effect upon him and that the muscular 
 tremor which attended his disease was for several hours 
 after each exposure much less violent. 
 
 The next series of experiments was with growing 
 animals to determine the effect, if any, of the alternating 
 magnetic stress in retarding or accelerating their growth. 
 Experiments of this nature also have been carried on at 
 the laboratory almost continuously for the past two years. 
 
 / ^Itema-tint current' ?na,inf 
 
 Q/ Ju/~i t c h 
 
 3 Tlmfiere meter* 
 
 Coils enclosing t/ie an i ma fa 
 
 Fig. 50. 
 
 Some of the time the animals used were rabbits and at 
 other times guinea pigs. As soon as one or more litters 
 of young rabbits or guinea pigs were old enough 
 to be separated from their mothers, they were di- 
 vided into two bunches as nearly alike in age and weight 
 as possible, and were carefully weighed. The two 
 bunches were placed in conditions of living in all re- 
 spects similar except that from five o'clock in the evening 
 until midnight one bunch was placed in a cage (Fig. 50) 
 made of the kind of wire above mentioned through which 
 an alternating five ampere current, with the frequency of 
 alternations above mentioned was passing, and the other 
 bunch was placed in an exactly similar coil which was not 
 
OF ELECTROTHERAPEUTICS. 155 
 
 connected with the current circuit. This plan was pursued 
 with each group of animals selected until they had reached 
 their full growth, or from six to twelve weeks, according 
 to the age of the animals at the commencement of the ex- 
 periment. The laboratory notes contain the weekly record 
 of the weight of each of the groups of animals experi- 
 mented upon in this manner. The interesting conclusion 
 that has been reached so far from these experiments, 
 which are still in progress, is that the group of animals 
 immersed in the alternating magnetic field without excep- 
 tion began, after the first week, to outstrip the other group 
 in weight, and a gain of from eighteen to twenty-four 
 per cent, in favor of the animals within the magnetic 
 field was observed each succeeding week until they neared 
 the period of full development, at which time the weekly 
 gain was less. During the two years in which these experi- 
 ments have been going on, ten separate groups of animals 
 have been used either in the magnetic field or as controls, 
 each group containing from three to five animals, and 
 uniformly those placed in the magnetic field gave evidence 
 for the first few weeks of accelerated nutritive action. In 
 the case of two of the groups, when the experiment was con- 
 tinued beyond eight weeks, the curve of increase shown by 
 the magnetized animals, which until eight weeks ran twenty 
 per cent, higher than that -of the other group, gradually 
 declined and at the end of the twelfth week their weight 
 had fallen a little below that of the other group. 
 
 It is an interesting fact that the janitor who has charge 
 of these animals and is a shrewd observer, but without 
 knowledge as to the purpose of the experiment, called our 
 attention to the fact that the group of animals that was 
 placed within the magnetic field spent much more time in 
 sleep during the day time, that is when the current was- 
 
1 56 ' LABORATORY MANUAL 
 
 withdrawn, than did the other group, but in no other re- 
 spect except the increase in weight did he nor we notice 
 any difference in their appearance or conduct. 
 
 As far as these experiments go they appear to show 
 that alternating magnetic stress is in some way related to 
 a quickened metabolism of tissue; that magnetic energy 
 goes through some transformation and appears as physio- 
 logical energy. 
 
 These results are very similar to those reported by 
 d'Arsonval and others as resulting from what that observer 
 lias termed auto-conduction brought about by high-tension 
 high frequency currents and as the apparatus employed by 
 d'Arsonval is not unlike that which we have employed in 
 these experiments, although the description of d'ArsonvaPs 
 experiments was not published until some months after we 
 had begun those we have been describing, it is not improb- 
 able the effects we have observed are due to the same cause. 
 There is this difference to be noted, however, that while 
 the currents employed by d'Arsonval were of the high- 
 potential and high-frequency character, the current em- 
 ployed by us was of only 52 volt pressure and the 
 frequency of alternations but 248 per second. 
 
THE THERMO-ELECTRIC GENERATOR. 
 
 (T. 419, 425.) 
 
 In 1822 it was discovered that an electric current could 
 be generated by heating the point of contact of two dissim- 
 ilar metals. Later it was found that if a number of points 
 of union of such metals were so arranged that alternate 
 junctions could be heated the E. M. 
 F. would be increased. This is 
 therefore a method whereby heat is 
 directly transformed into electric 
 energy in the form of a direct cur- 
 rent. The accompanying figure 
 represents a thermo-electric gener- 
 ator employing these principles 
 which is capable of producing elec- 
 tric currents of sufficient strength 
 and intensity for various practical 
 applications. The heat furnished 
 by the combustion of gas flowing Fig. 51. 
 
 from an ordinary gas burner and the parts other than the 
 points of junction of the dissimilar metals are kept cool by 
 allowing a stream of water to flow through the apparatus. 
 The generator tested in this laboratory has an E. M. F, 
 of 6 volts and furnishes a current somewhat exceeding 
 3 amperes. The output of energy is subject to very slight 
 variations. The following are some of the therapeutic 
 applications to which such a source of electric energy 
 furnishing a current of this nature would be adapted: 
 
'58 
 
 LABORATORY MANUAL 
 
 i. It would heat electric cauteries having com- 
 paratively fine wires, or would light some of the 
 
 smaller varieties of medical 
 exploring lamps. 
 
 2. It could be used to 
 excite a medical induction 
 coil. 
 
 3. By employing a good 
 low voltage electric motor it 
 could be used to run various 
 mechanical devices needed in 
 the physician's or dentist's of- 
 fice. 
 
 Owing to the low E. M. 
 F. of the current it could not 
 be conveyed through the tissues of the body so as to do 
 effectively any of the work which we have discussed under 
 the head of electrolysis, phoresis, or the physiological 
 action of the direct current. 
 
 ELECTRO-THERMIC GENERATORS. 
 
 We have considered (p. 56) electricity as a source of 
 heat for heating the electro-cautery. It was there stated 
 that whenever electricity is expended in overcoming resist- 
 ance it reappears in the form of heat or radiant energy. 
 Many applications of this principle may be made in thera- 
 peutics in addition to that of the electro-cautery. 
 
 When a constant source of electric energy is conve- 
 niently at hand as is the case in many hospitals as well as 
 in private houses at the present time, a steady and equable 
 .application of heat may be made to a patient, when it is 
 
OF ELECTROTHERAPEUTICS. 
 
 '59 
 
 needed, by some suitable arrangement for transforming 
 electric energy into heat. The accompanying figure illus- 
 
 Fig. 53. 
 
 trates one of these in the form of a pliable and adjustable 
 pad. It consists of two sheets of asbestos with wire im- 
 bedded in them enclosed in a cover of flannel. When at- 
 tached by conducting wire cords to the socket of an 
 incandescent lamp the temperature of the pad can be 
 raised to any degree desired and there maintained for any 
 length of time. An appliance for this purpose can utilize 
 either an alternating or direct current. 
 
TABLE OF CONTENTS. 
 
 Amalgamating fluid, 21 
 
 Amalgamation, 21 
 
 Ampere,.... 22, 23, 39 
 
 Anaphoresis 51 
 
 Anelectrotonus, 54 
 
 Anions, 39 
 
 Anode, 39 
 
 Apostoli, 118 
 
 Auto conduction, 
 
 Batteries, body, 9 
 
 " notes on, 20 
 
 " portable, 20 
 
 Eattery, experimental, 27 
 
 " . storage, 63 
 
 Bichromate cell, 17 
 
 " solution, 10, 18 
 
 Breeze, electric or static, 
 
 126, 133, 141 
 
 Brush discharge, 126 
 
 Bunsen cell, ... 16 
 
 Calibration, 2, 3 
 
 Catalysis, 55 
 
 Cataphoresis, 51 
 
 Catelectrotonus, 54 
 
 Cathions, 39 
 
 Cathode, 39 
 
 " ray, 146 
 
 Cautery, Galvano, 56 
 
 " sources of current 
 
 for, 59 
 
 Cautery transformer, 104 
 
 Cell, bichromate 17 
 
 ' Bunsen, 16 
 
 ' chloride of silver, 20 
 
 ' Daniell, II, 15 
 
 ' gravity, 15 
 
 ' Leclanche,.... 18 
 
 C harri n, 117 
 
 Chemical reaction of cells, 14 
 
 Circuit, 14 
 
 " divided, ... 34 
 
 '' open, 14 
 
 " short, 14 
 
 Coil, induction, 73, 77 
 
 '' physician's induction,.... 76 
 
 " primary, 77 
 
 " secondary, 82 
 
 Combination method of join- 
 ing cells, 24, 26 
 
 Controller, current, 37, 38 
 
 Crookes tube, 73, 148, 150 
 
 Cry ptoscope, 1 49 
 
 Current, 7, 22 
 
 " density, 38 
 
 " direct, 85 
 
 " direction of, 8 
 
 " galvanic, 85 
 
 Current, high-potential and 
 high-frequency,.. ..105, 113, 145 
 
 Current, induced, 86, 87 
 
 '' magnetic effects of,.. 64 
 
 " "second order", 109 
 
 " sinusoidal, 91 
 
 Current, sinusoidal physiolog- 
 ical action of, 95 
 
 Daniell cell, n, 15 
 
 D'Arsonval, 
 
 106, 113, 117, 119, 121 
 
 Density of current, 38 
 
 Direct spark, 130, 140 
 
 Disruptive discharge coil, 145 
 
 Dubois Raymond coil, 83 
 
 Edison,.. 149 
 
 Electric belts, 9 
 
 " breeze, 126, 133, 141 
 
 " osmose, 51 
 
 plasters 9 
 
 Electrical units, 22, 23 
 
 Electrode, directive, 135 
 
 Electrolysis, 39 
 
 '' rules for,.. 42 
 
 Electrolyte, 39 
 
 Electromotive-force 22 
 
 Experimental battery, 27 
 
 Faradic coil, (see induction 
 coil) 80 
 
l62 
 
 TABLE OF CONTENTS. 
 
 Fluid, battery, 18 
 
 Fluorescent screen, 143, 149 
 
 Fluoroscope, 149 
 
 Friction spark, 134, 141 
 
 Galvanic coil, 4 
 
 '' current, 85 
 
 Galvano cautery, 56 
 
 Galvanometer, 2 
 
 Generator, thermo electric,... 157 
 
 Hertz, 112, 113 
 
 High potential currents, ...105, 113 
 High potential currents, ther- 
 apeutics of n3 
 
 High tension, high-frequency 
 
 current, 145 
 
 Holder, plate, 5 
 
 Holt/ machine, T22, 123 
 
 Impulsive discharge, 106 
 
 Indirect spark, 133, 141 
 
 Induction coil, 73, 77 
 
 " current, 73 
 
 Insulation, positive, 140 
 
 '' static, I2Q 
 
 In terrupte r , 80 
 
 Ions, 39 
 
 Kennelly sinusoidal machine, 100 
 
 Leclanche cell, 18 
 
 Light, electric, 62 
 
 Local action, 21 
 
 Magnet, temporary, 78 
 
 Magnetic effects of current,... 09 
 
 " field, alternating, 151 
 
 '' flux, 101 
 
 Magnetism, 67 
 
 Magnetism, relation to living 
 
 organism, I'5I, 152 
 
 Magneto-electric machine 90 
 
 Magneto- motive force, 101 
 
 Mclntosh sinusoidal appa 
 
 ratus 97 
 
 Medical induction coil,... 74 
 
 Milliampere, i 
 
 Milliampere-meter, physi 
 
 cians, 3 
 
 Morton, Dr 13? 
 
 Multiple arc, 24 
 
 Needle spray, 13 
 
 Ohm, 22, 23 
 
 Ohm's law, 22 
 
 Osmos, electric, '51 
 
 Phenol -phthalein, 45 
 
 Physiological effects of direct 
 
 currents, 53 
 
 Physiological effects of high 
 
 tension currents, 113 
 
 Physiological effects of -sinu- 
 soidal currents, 95 
 
 Physiological effects of static 
 
 electricity, 128 
 
 Plate, collecting, 13 
 
 " generating, . 13 
 
 Pole changer, 34 
 
 Poles, 13 
 
 Polarization, batteiy, 10, II 
 
 " effects of,. 12 
 
 '< to prevent, 12 
 
 Primary induced current, 86 
 
 Problems, 47, 48, 49, 50 
 
 Rabbits, experiments with in 
 
 magnetic fields, 153 
 
 Reactions, chemical, of cell's, 14 
 
 Reluctance, .' TOI 
 
 Resistance, 22 
 
 body, 33 
 
 internal, 32 
 
 joint, 55 
 
 laws of, 46 
 
 specific, 46 
 
 unknown, 33 
 
 Rheostat, graphite, . 51 
 
 Rhumkorff coil, 144 
 
 Rontgen rays, 73, 142 
 
 Rontgen rays, diagnosis by,... 142 
 
 " " generations for, 143 
 
 Rotary transfoVmer, 65 
 
 Salvioni, 149 
 
 Screen, fluorescent, 143 
 
 Secondary induced current,... 87 
 
 Sensitized plates, 149 
 
 Series, 24 
 
 Shunt, 35 
 
 " current controller,... . 37. 38 
 
 Sine curve, 9 2 
 
 Sinusoidal apparatus, Mcln- 
 tosh, 97 
 
 Sinusoidal apparatus, Ken- 
 nelly loo- 
 
 Sinusoidal current, 91 
 
 Sinusoidal current, physiolog- 
 ical and therapeutic uses of. 95- 
 
TABLE OF CONTENTS. 
 
 163 
 
 Skiagraph, 145, 146 
 
 Soldering, 9 
 
 Spark, direct, 130, 140 
 
 " friction...... 134, 141 
 
 " indirect, 133, 141 
 
 Spray 135 
 
 Static electricity, physiolog- 
 ical action of, 128 
 
 Static induced current, 
 
 ., 124, 136, 142 
 
 Static insulation or charge 129 
 
 Static machine, 121 
 
 Storage battery, 63 
 
 Tesla, Nikola, 106, 113 
 
 Thermo electric generator, 157 
 Thermo-electric generator, 
 
 uses of 158 
 
 Thompson, Elihu, 106, 113 
 
 Topler, 122 
 
 Toxines, bacterial, 117 
 
 Tubes, vacuum, 146 
 
 Tungstate of calcium, 149 
 
 Unicellular organisms, ....;.... 116 
 Units, electrical, 22, 23 
 
 Vacuum, 147 
 
 " tubes, 146 
 
 " (l action in, 148 
 
 Volt, 22, 23 
 
 Volta pile, 8 
 
 Valtaic cell, . 4 
 
 Voltmeter, 8 
 
 Wimshurst machine, 122, 124 
 
 X-rays, 142, 146 
 
 " experiments, 150 
 
 Zinc, chemically pure, 6 
 
 " commercial, (> 
 
f\ LIST OF BOOKS 
 
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 ANN ARBOR. 
 
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 BO WEN. A Teachers'* Course in Physical Training. By Wilbur P. 
 Bowen, Director of Physical Training, Michigan State Normal Col- 
 lege. In Press. 
 
 CHEEVER. Select Methods in Inorganic Quantitative Analysis. By 
 Byron W. Cheever, A.M., M.D., late Acting Professor of Metal- 
 lurgy in the University of Michigan. Revised and enlarged by Frank 
 Clemes Smith, Professor of Geology, Mining and Metallurgy in the 
 State School of Mines, Rapid City, S. D. Parts I. and II. Third 
 edition. i2mo. $1.75. 
 
 The first part of this book, as indicated by the title, consists of Laboratory Notes 
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 Gravimetric and Volumetric Analysis, for beginners, by means of the chemical 
 analysis of a set of substances, properly numbered, in each case giving the methods 
 to be followed in such analysis; also the methods for calculating; and preparing 
 volumetric standard solutions, generally following the course offered by Professor 
 Cheever to his students. It also considers the methods for the determination of the 
 specific gravities of various liquids and solids. 
 
 Although a number of the analyses contained in Part I. may be of only approxi- 
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 ner simply serves to emphasize the necessity of careful scrutiny of details and 
 methods for practical work in the future. 
 
 Part J. is offered, then, for the use of schools and colleges, and it is intended to 
 supply a source of elementary information upon the subject of Quantitative Chemi- 
 cal Analysis rarely offered in such form in works upon that subject. Preface. 
 
 The author was for many years Professor of Metallurgy in the University of 
 Michigan, and the methods here presented are those mostly offered by him to his 
 students. As a beginner's book in quantitative analysis, it will be found eminently . 
 practical, and it can be honestly recommended to the student who desires a source 
 of elementary information upon this branch of applied science. The book is divided 
 into two parts, the first consisting of laboratory notes for beginners. The subjects 
 of gravimetric and volumetric analysis are considered by means of the chemical 
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 to be followed in such analysis, and also the methods of calculating and preparing 
 volumetric standard solutions, etc. Methods for the determination of specific 
 gravities of various liquids and solids are also considered. 
 
 Part II. contains a number of select methods in inorganic quantitative analysis, 
 such as the analysis of limestone, iron ores, manganese ores, steel, the analysis of 
 
coal, water, mineral phosphates, smelling ores, lead slags, copper, arsenic, bismut h, 
 etc. A chapter on reagents concludes the work. Pharmaceuucnl K>a. 
 
 DEWEY. 7^> Study of Ethics. A Syllabus. By jonn Dewey, Pro- 
 fessor of Philosophy in the University of Chicago. Octavo. 144 
 pages. Cloth, $1.25. 
 
 D'OOGE. Helps to the Study of Classical Mythology; for the Lower 
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 Michigan State Normal College. 12 mo. 180 pages. Cloth. 45 cents. 
 
 A bibliography based ou practical experience. The author is a professor in the 
 Michigan State Normal College. As the myths of all nations manifest themselves 
 first in religion, secondly in art, and third in literature, these reading references are 
 grouped in the above classes. One section is devoted to the study of mythology in 
 the grades, and an introductory chapter gives hints for teaching the subject in the 
 lower grades. The books suggested in the body of the work are given in one alpha- 
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 references, and a good general index. Publishers Weekly, 
 
 DOW. Brief Outlines in European History. A Syllabus for the Use of 
 Students in History, Course /., in the University of Michigan. By 
 Earl Wilbur Dow. 41 pages. Pamphlet, 35 cents. 
 
 DOW.rief Outlines in European History. A Syllables for the Use of 
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 DZIOBEK. Mathematical Theories of Planetary Motions. By Dr. 
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 Berlin, Charlottenburg. Translated by Mark W. Harrington, for- 
 merly Chief of the United States Weather Bureau, and Professor of 
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 Michigan, President of the University of Washington, and Wm. J. 
 Hussey, Assistant Professor of Astronomy in the Leland Stanford, 
 Jr. University. 8vo. 294 pages. $3.50. 
 
 The determination of the motions of the heavenly bodies is an important problem 
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 ment of mathematics. It has engaged the attention of the greatest mathematicians, 
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 displayed unsurpassed ingenuity. The methods devised by them have proved use- 
 ful, not only in this problem, but have also largely determined the course of advance 
 in other branches of mathematics. Analytical mechanics, beginning with Newton, 
 and receiving a finished clearness from Lagrange. is especially indebted to this 
 problem, and in turn, analytical mechanics has been so suggestive in method as to 
 determine largely both the direction and rapidity of the advancement of mathemat- 
 ical science. 
 
 Hence, when it is desired to illustrate the abstract theories of analytical mechan- 
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 heavenly bodies, its powerful influence on the historical development of this 
 science, and finally the dignity of its object, all point to it as most suitable for this 
 purpose. 
 
 This work is intended not merely as an introduction to the special study of 
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 FORD. The Cranial Nerves. 12 pairs. By C. L. Ford, M.D., late 
 Professor of Anatomy and Physiology in University of Michigan. 
 Chart, 25 cents. 
 
FORD. Classification of the Most Important Muscles of the Human 
 Body, With Qrigin Insertion, Nervous Supply and Principal Action 
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 FRANCOIS. Les Aventures Du Dernier Abencerage Par Chateaubri- 
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 cents. 
 
 GRAY. Outline of Anatomy. A Guide to the Dissection of the Htiman 
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 HERDMAN-NAGLER. A Laboratory Manual of Electrotherapetitics. 
 By William James Herdman, Ph.B., M.D., Professor of Diseases of 
 the Nervous System and Electrotherapeutics, University of Michigan, 
 and Frank W. Nagler, B.S., Instructor in Electrotherapeutics, Uni- 
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 $1.50. 
 
 It has been our experience that the knowledge required by the student of medi- 
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 This has been the plan adopted for teaching electrotherapeutics at the Univer- 
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 that will permit for it a wider usefulness as well as gain for it in the intelligent criticism 
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 HOWELL. Directions for Laboratory. Work in Physiology for the Use 
 of Medical Classes. By W. H. Howell, Ph.D., M.D., Professor of 
 Physiology and Histology. Pamphlet. 62 pages. 65 cents. 
 
 HUBER. Directions for Work in the Histological Laboratory. By G. 
 Carl Huber, M.D., Assistant Professor of Histology and Embry- 
 ology, University of Michigan. Second edition, revised and enlarged. 
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 It is adapted for classes in medical schools and elsewhere where it is desired to 
 furnish the class with material already prepared for the demonstration of structure 
 rather than to give instruction in the technique of the laboratory Provision for the 
 
latter is made, however, by the addition of a section of about 50 pages on the meth- 
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 cellent plate of blood elements. The selection of methods has in the main been 
 judicious. The exposiiions are both clear and concise. Journal of Comparative 
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 In this little book Dr. Huber has given us a model manual of microscopical tech- 
 nique in the laboratory study of histology. The subject matter is divided into con- 
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 of the University of Michigan. 8vo., 735 pages. Full law sheep 
 s binding. $3.75. 
 
 Several years of experience as an instructor has taught the author that the best 
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 MONTGOMERY-SMITH. Laboratory Manual of Elementary Chem- 
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 by F. N. Cole, Ph.D., formerly Assistant Professor of Mathematics 
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 NOVY. Laboratory Work in Physiological Chemistry. By Frederick G. 
 Novy, Sc.D., M.D., Junior Professor of Hygiene and Physiological 
 Chemistry, University of Michigan. Second edition, revised and 
 enlarged. With frontispiece and 24 illustrations. Octavo. Cloth, 
 $2.00. 
 
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 within a very short time after the publication of the first. The first chapters deal 
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 the gastric juice, the pancreatic secretion, the bile, blood, milk, and urine, while the 
 closing chapter deals with a list of reagents. 
 
 While the book is manifestly designed for the use of Dr. Novy's own students, we 
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 method in physiological chemistry ought to be carried out, had of necessity to refer 
 to a German text-book. This comparatively small book for it only covers some 
 three hundred pages gives as good a general account of ordinary laboratory methods 
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 say that the book has undoubtedly been written by one who has worked out the 
 methods and knows the importance of exact practical details Edinburgh Med, 
 Jour., Scotland, 
 
Physiological chemistry is one of the most important studies of the medical curri- 
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 The rapid development of this department of science within a few years past has 
 thrown much and needed light upon physiological processes. It is from this quarter 
 and from bacteriological investigations that progress must chiefly be expected. The 
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 Few are better prepared to write such a book than Dr. Novy, who has himself done 
 much original work in this field. The Medical Bulletin, Philadelphia. 
 
 This is a greatly enlarged edition of Dr. Novy's work on Physiological Chemistry, 
 and contains a large amount of new material not found in the former edition. It is 
 designed as a text-book and guide for students in experimental work in the labora- 
 tory, and does not therefore cover the same ground as the works of Gamgee, Lea, 
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 should be adopted by our medical colleges throughout the country, because it is an 
 American production, contains only such directions and descriptions as have been 
 verified by actual practice with students, and because it is clear, concise and definite 
 in all its statements. Its first ten chapters treat of fats, carbohydrates, proteins, 
 saliva, gastric juice, pancreatic secretion, bile, blood, milk, a^d urine. Chapter xi. 
 is devoted to the quantitative analysis of urine, milk, gastric juice, and blood, while 
 chapter xii. gives tables for examination of urine and a list of reagents. Am. 
 Medico- Surgical Bulletin, N. Y. 
 
 NOVY. Laboratory Work in Bacteriology. By Frederick G. Novy, Sc. 
 I)., M.D., Junior Professor of Hygiene and Physiological Chemistry, 
 University of Michigan. Second edition, entirely rewritten and 
 enlarged, 563 pages. Octavo. $3.00. 
 
 As a teacher of bacteriology, the author has had extensive experience, and the 
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 will serve to show the scope of the work: Form and Classification of Bacteria; Size 
 and Structure of Bacterial Cell; Life History of Bacteria; Environment of Bacteria; 
 Chemistry of Bacteria; the Microscope; Cultivation of Bacteria; Non-Pathogenic 
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 Relation of Bacteria to Disease Methods of Infection and Examination; Patho- 
 genic Bacteria; Yeasts. Moulds and Streptotrices; Examination of Water, Soil and 
 Air; Special Methods of Work. To the latter subject, two chapters are devoted, 
 in which are very fully outlined various special methods of value to advanced 
 students. Pharmaceutical Era, N. Y. 
 
 STRUMPELL. 6/W/ Guide for the Clinical Examination of Patients. 
 Compiled for the Practical Students of the Clinic, by Professor Dr. 
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 PREFACE TO THE SECOND EDITION. The seccnd edition of this book has been 
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 to learn a systematic examination of the patient, and to impress on him the most 
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 SUNDERLAND. ^-(J;/^ Upward Look Each Day. Poems of Hope and 
 Faith. Selected by J. T. Sunderland. Third Edition, 16 mo. 
 White Binding, 30 cents; Cloth, 40 cents; Full morocco, 75 cents. 
 
 SUN D E R L AN D Grains of Gold. Some Thoughts and a Brief Prayer 
 For Each Day of the Monllis. Designed as Daily Helps in the 
 Higher Life. Compiled by J. T. Sunderland. White Binding, 35 
 cents, 
 
WARTHIN. Practical Pathology for Students and Physicians. A 
 Manual of Laboratory and Post-Mortem Technic, Designed Espe- 
 cially for the Use of Junior and Senior Students in Pathology at 
 the University of Michigan. By Aldred Scott Warthin, Ph.D., M. 
 D., Instructor in Pathology, University of Michigan. Octavo. 234 
 pages. Cloth. $1.50. 
 
 We have carefully examined this book, and our advice to every student and prac- 
 titioner of medicine is buy it. You will never regret having invested your money in 
 it, and you will acquire such a large fund of information that the study of pathology 
 will become a pleasure instead of the drudgery which it sc unfortunately seems to 
 be in many cases. 
 
 Part I. of this book, embracing some 103 pages, deals with the materials, which 
 includes the proper examination and notation of the gross changes which have 
 occurred in every part of the body. In fact it is a complete expose of what a com- 
 plete and accurate autopsy should be, the observance of which is oftener followed 
 in the breach than in the actuality. Part II., which includes 134 pages, deals with 
 the treatment of the material. This is a very important part of the work, as it gives 
 explicit directions in regard to the instruments to use, stains and staining methods, 
 drawing, the preservation of specimens, Hardening methods, in fact, of all those 
 technical points connected with practical pathological microscopy. The examina- 
 tion of fresh specimens, injections, methods fixing specimens as well as special 
 staining methods are taken up. In fact, space forbids us to give the entire, which 
 are most valuable in every detail. St. Loui* Medical and Surgical Journal. 
 
 WATSON. Tables for the Calculation of Simple or Compound Interest 
 and Discount and the Averaging of Accounts. The Values of 
 Annuities^ Leases, Interest in Estates and the Accumulations and 
 Values of Investments at Simple or Compound Interest for all Rates 
 and Periods; also Tables for the Conversion of Securities and Value 
 of Stocks and Bonds. With full Explanation for Use. By James 
 C. Watson, Ph.D., LL.D. Quarto. Cloth, $2.50. 
 
 A book most valuable to bankers, brokers, trustees, guardians, judges, lawyers, 
 accountants, and all concerned in the computation of interest, the division and set-" 
 tlement of estates, the negotiation of securities, or the borrowing and lending of 
 money, is the above work of the late Professor James C. Watson, formerly Director 
 of the Observatories and Professor of Astronomy at the Universities of Michigan 
 and Wisconsin, and Actuary of the Michigan Mutual Life Insurance Company. 
 
 It contains, in addition to the usual tables for the calculation of simple or com- 
 pound interest and discount, many tables of remarkable value, not found elsewhere, 
 for the averaging of accoutns, the values of annuities, leases, interests in estates, 
 and the accumulations and values of investments; also tables for the conversion of 
 securities, and the values of stocks and bonds. 
 
 There are also given very full and clear explanations of the principles involved in 
 financial transactions, and a great variety of miscellaneous examples are worked 
 out in detail to illustrate the problems arising in interest, discount, partial payments, 
 averaging of accounts, present values, annuities of different kinds, annual payments 
 for a future expectation (as in life insurance), or for a sinking fund, conversion of 
 securities, values of stocks and bonds, and life interests. 
 
 This book was issued from the press under the author's careful supervision. 
 Professor Watson was noted for his clear insight into problems involving computa- 
 tions, and also for his wonderful ability in presenting the method of solution of such 
 problems in a plain and simple manner. The varied array of practical examples 
 given in connection with his " Table " shows these facts in a remarkable manner. 
 This book provides, for those least expert in calculations, the means of avoiding 
 mistakes likely to occur ; and for the man engrossed in the cares of business, the 
 means of making for himself, with entire accuracy, the calculation which he may 
 need, at the moment when it is needed. 
 
 WRENTMORE-GOULDING. A Text-Book of Elementary Mechan- 
 ical Drawing for Use in Office or School. By Clarence G. Wrent- 
 more, B.S., C.E., and Herbert J. Goulding, B.S., M.E., Instructors 
 in Descriptive Geometry and Drawing at the University of Michigan. 
 Quarto. 109 pages and 165 cuts. $1.00. 
 
 This book is intended for a beginners course in Elementary Mechanical Drawing 
 for the office and school. Illustrations have not been spared, and the explanations 
 have been made in a clear and concise manner for the purpose of bringing the stu- 
 
othe desired results by the shortest route consistent with the imparting of an 
 accurate knowledge of the subject. 
 
 The first chapter is devoted to Materials and Instruments; the second chapter, 
 Mechanical Construction; third chapter, Penciling. Inking, Tinting; fourth chap- 
 ter, Linear Perspective; fifth chapter, Teeth of Grass. 
 
 WRENTMORE. Plain Alphabets for Office and School. Selected by 
 C. G. Wrentmore, B.S., C.E., Instructor in Descriptive Geometry 
 and 'Drawing, University of Michigan. Oblong. 19 plates. Half 
 leather, 75 cents. 
 
 Souvenir of the University of Michigan, Ann Arbor. Containing 38 
 photo-gravures of President James B. Angell, prom.nent University 
 Buildings, Fraternity Houses, Churches, Views of Ann Arbor, Etc., 
 Etc. Done up in blue silk cloth binding. Price, 50 cents, postpaid. 
 
 Physical Laboratory Note Book. A Note Book for the Physical Lab- 
 oratory. Designed to be used in connection with Chute's Physical 
 Laboratory Manual. Contains full directions for keeping a Physical 
 Laboratory Note Book. 112 pages of excellent writing paper, ruled 
 in cross sections, Metric System, size 7 x 9^ inches. Bound in full 
 canvass, leather corners. Price, by mail, 30 cents. Special prices 
 to Schools furnished on application. 
 
 Botanical Laboratory Note Book. A Note Book for the Botanical Lab- 
 oratory. Contains directions for Botanical Laboratory. 200 pages 
 of best writing paper, ruled with top margins. Pocket on inside of 
 front cover for drawing cards. Bound in substantial cloth cover and 
 leather back. Size 6x9^. Price, by mail, 35 cents. Special prices 
 to schools furnished on application. 
 
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 THE UNIVERSITY OF CALIFORNIA LIBRARY