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 OF THE 
 
 PROGRESS AND PRESENT STATE 
 
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 PROGRESS AND PRESENT STATE 
 
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 Animal Cfjemfsttp, 
 
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 IONS JACOB BERZELIUS, M. D, 
 
 Professor of Medicine and Pharmacy, c. &c. 
 Translated from the Swedish, 
 
 BT 
 
 GUSTAVUS BRUNNMARK, D,D. 
 
 Chaplain to the Swedish Legation at the Court of St. James's. 
 
 llontum : 
 
 Printed by J. Skirven, Ratcliff Highway ; 
 AND SOLD BY 
 
 JOHN HATCHARD, 190, Piccadilly; J. JOHNSON and Co. St, Paul's 
 Church Yard 5 and T. BOOSEY, 4, Broad Street, 
 
 : 1813. : \ ; 
 
TH- 
 
 BIOLOGY 
 LIBRARY 
 
PREFACE. 
 
 
 THE Royal Academy of Sciences at Stock* 
 holm elects its President every half year from 
 among its Members ; and it is required, by the 
 statutes of the Academy, that whoever has filled 
 that office should, upon leaving it, read an Essay 9 
 or deliver a Speech, on some literary or scientific 
 subject of his own choice. This regulation gave 
 rise to the present Treatise, the Author of 
 which has occupied himself very much with in- 
 vestigations in Animal Chemistry, and> several 
 years ago, published a Work, in two volumes, 
 on this new branch of Science. In the year 
 1810, when he gave up his f residency in 
 
 248111 
 
VI. PREFACE. 
 
 the Academy, he chose for his subject, a View of 
 the Progress and present State of that Science, 
 combining what he had himself investigated , 
 with what he had derived from the scattered 
 Works of other Chemical Writers. 
 
 As very few of Prof essor BERZELIUS'S Publi- 
 cations have been translated into other languages, 
 and none of them has, as yet, appeared in a com- 
 plete state in English, the Translator of this lit- 
 tle Work flatters himself, that he is doing a not 
 unacceptable service to the British literary Pub- 
 lic, at the same time that he feels great pleasure 
 in having the honour to introduce his most par- 
 ticular friend to the nearer notice of those, who 
 may already be acquainted with his name. 
 
 If the translation, as it is hoped, has the me- 
 rit of being correct in a scientific point of view, 
 it is entirely owing to the kind assistance of two 
 literary friends, both members of the Royal So- 
 ciety Dr. THOMAS YOUNG, and Mr. WILLIAM 
 ALLEN, who have had the goodness to read through 
 and revise the whole. Dr, YOUNG was well ac~ 
 
PREFACE. vii. 
 
 qudinted with the original, from having been en- 
 gaged in abridging it for a work of his own : 
 Jfr. ALLEN'S familiarity with every department 
 of Chemistry, rendered him particularly well 
 qualified for the appreciating the accuracy of 
 chemical language; and the Translator takes 
 this opportunity of expressing to both these Gen- 
 tlemen his most sincere thanks, for their very va- 
 luable corrections. 
 

 
VIEW 
 
 OF THE 
 
 PROGRESS AND PRESENT STATE 
 
 OF 
 
 THE Royal Academy of Sciences having 
 honored me with so distinguished a mark of its con- 
 fidence, as to appoint me its President during the 
 last six months, I have only to regret, that, unac- 
 customed to such an office, I should not have 
 been able to do that justice to its choice, which 
 I have ardently wished; but I have always 
 flattered myself with the hope, that the Academy, 
 aware of my good intentions, would overlook 
 what was wanting in my abilities ; and that hope 
 has not deceived me. On giving up this day the 
 situation, which I have held, to a Gentleman*, 
 who, by his age, experience, a,nd learning, is so 
 
 * W. af Hisinger, 
 
2 
 
 much worthier than myself of that distinction 
 amongst you, I shall avail myself of the present 
 opportunity to occupy the attention of the Aca- 
 demy with some historical remarks on a Science, 
 in which, by much labour and attention, I have 
 acquired some information and experience, viz. 
 the Chemistry of the Animal Body ; and I will 
 shortly relate the progress which it has made 
 during these latter years. The facts which have 
 been ascertained in this science are interesting, 
 and the knowledge of them useful to every one ; 
 although the science, in its detail, can only be 
 followed up by such as make this branch of 
 Chemistry their peculiar study. 
 
 I shall not detain you with the history of 
 Animal Chemistry from remoter times; since the 
 
 relation of the mistakes of our Forefathers, and 
 
 i 
 
 the slow progress which every science has made, 
 interesting as it may be in the history of man, is 
 of little or no consequence in examining the 
 present state of any particular science. 
 
 Our forefathers began very early to explain 
 the phenomena of living nature, from observations 
 made upon inanimate matter : this gave rise to 
 particular Sects in medicine, which then, as now, 
 
were doomed to see their theories overturned 
 by experience. The very intricate composition 
 of animal matter, and the innumerable produc- 
 tions which, in various ways, may be obtained 
 from it, made it almost impossible, in the infancy 
 of chemical knowledge, to produce any accurate 
 analysis of it. It was not till after the discoveries 
 of a BLACK, and the lucid explanation of such 
 phenomena, as before his time \vere either 
 unknown or misunderstood. It was not till 
 after the reiterated and solid experiments, of 
 SCHEELE, and of PRIESTLEY, and the establish- 
 ment of the new theory, which LAVOISIER, as- 
 sisted by the labours of these predecessors, had 
 given to chemical science, that it was possible 
 to begin the examination of the interior ceconomy 
 of the animal body with any hope of success. 
 The facts, discovered by BLACK and LAVOISIER, 
 were now applied to Animal Chemistry, some- 
 times, it is true, with good effect, but often with 
 greater confidence in the general application of 
 the new doctrine, than experience afterwards 
 sanctioned. In this manner, the first scattered 
 Works were produced on this subject, the ag- 
 gregate information of which, constituted the 
 still new and infant Science of Animal Che- 
 mistry. 
 
The constituent parts of the animal body are 
 altogether the same as those found in unorga- 
 nised matter, and they return to their original 
 unorganic state by degrees, partly during the 
 progress of life, partly when the body, after death, 
 undergoes its final change. And independently 
 of this, there exist processes between the unor- 
 ganic constituent, or elementary particles within 
 the animal body, which have sometimes not the 
 least resemblance to those we see in unorganised 
 matter. We may consider the whole animal 
 Body as an instrument, which, from the nourish- 
 ment it receives, collects materials for continual 
 chemical processes, and of which the chief object 
 is its own support. But, with all the knowledge 
 we possess of the forms of the body, considered 
 as an instrument, and of the mixture and mutual 
 bearings of the rudiments to one another, yet the 
 cause of most of the phenomena within the Ani- 
 mal Body lies so deeply hidden from our view, 
 that it certainly will never be found. We call 
 this hidden cause vital power; and like many 
 others, who before us have in vain directed their 
 deluded attention to this point, we make use of 
 a word to which we can affix no idea. This 
 power to live belongs not to the constituent parts 
 of our bodies, nor does it belong to them as an 
 
ns trument, neither is it a simple power; but the 
 result of the mutual operation of the instruments 
 and rudiments on one another a result, which 
 varies as the operations vary, and which often, 
 from small changes and obstructions, ceases alto- 
 gether. When our elementary books inform us, 
 that the vital power in one place produces from 
 the blood the fibres of the muscle ; in another, a 
 bone ; in a third, the medulla of the brain ; and 
 in another again, certain humours, which are des- 
 tined to be carried of; we know after this expla- 
 nation as little as we knew before. 
 
 This unknown cause of the phenomena of life 
 is principally lodged in a certain part of the Ani- 
 mal Body, viz. in the nervous system, the very 
 operation of which it constitutes. The brain and 
 the nerves determine altogether the chemical 
 processes which occur within the body : and al- 
 though it cannot be denied that the exercise of 
 their functions tends to produce chemical effects ; 
 yet we are constrained to confess, that the che- 
 mical operations therein are so far beyond our 
 reach, that they entirely escape all our observa- 
 tions. Our deepest chemical researches, and the 
 finest discoveries of later times, give us no in- 
 formation on this subject. Nothing 1 of what Che* 
 
 B 3 
 
6 
 
 mistry lias taught us hitherto, has the smallest 
 analogy to the operation of the nervous system, 
 or affords us the least hint toward a knowledge of 
 its occult nature. And the chain of our experi- 
 ence must always end in something inconceiv- 
 able; unfortunately, this inconceivable something 
 acts the principal part in Animal Chemistry, and 
 enters so into every process even the most mi- 
 nute, that the highest knowledge which we can 
 attain, is the knowledge of the nature of the pro- 
 ductions, whilst we for ever are excluded from 
 the possibility of explaining how they are pro- 
 duced. Permit me here to shew by an example 
 the embarrassment of the studenj: of Animal Che- 
 mistry on all occasions, when the inconceivable 
 nervous system exercises its operations : It is 
 well known that blood, which is always formed 
 from the food of the animal, is the raw material 
 out of which the body recruits and re-produces its 
 parts; and that this blood, which is every where 
 of the same nature, is conveyed through the ar^ 
 teries to the different parts of the body. From 
 this blood the kidneys form urine ; the glands near 
 the ear and under the tongue, saliva; those in the 
 breasts of women, milk; and so forth: all which 
 are humours of the most different nature. The 
 most acute anatomical investigation has proved, 
 
beyond all doubt, that the vessels in these parts, 
 while they extend themselves, proceed in an un- 
 interrupted course, without communicating with 
 any others that no foreign humours which could 
 affect the blood, have access to them ; and that 
 consequently the blood is not exposed to the in- 
 fluence of any mixed chemical agency. But what 
 is it that here effects the chemical process, which, 
 from the very same particles of the blood, forms 
 those of saliva, milk, and urine? It cannot be 
 form and flexure of the vessels, since that can 
 only cause a greater or less delay ; and that this 
 alone cannot determine the formation of the se- 
 creted matter, common Chemistry will shew. 
 Consequently, there remains only the influence 
 of the nerves, which enter into these parts, and 
 which determine as well the nature of the se- 
 creted matter as its quantity ; but until our ex- 
 periments on unorganised matter shall have fur- 
 nished us with a chemical phenomenon, which 
 has any analogy with the operations of the nerves 
 on these occasions, \ve shall never be able to dis- 
 cover the laws of those operations, nor explain 
 the intimate nature of these processes. And if the 
 knowledge of the transformation of the blood 
 into other humours, which knowledge does in 
 itself bear an analogy to chemical phenomena 
 
8 
 
 in general, is so deeply hidden from our view, 
 how shall we attempt to explain the renewal of 
 the solid animal parts, whereby the body is sup^ 
 ported during the constant exchange of its ele- 
 ments ? But still more astonishing are the opera- 
 tions of the brain . How amazing, that our thought, 
 even in its sublimest flight, and when it pene- 
 trates the most hidden recesses of nature, should 
 depend on a previous chemical process, which, if 
 in the least disturbed as to its correctness, would 
 distract this very thought, change it into mad^ 
 ness, or make it cease altogether ; and yet this is 
 an incontrovertible truth. But is it not probable, 
 that human understanding", which is capable of so 
 
 uch cultivation, which has calculated the laws 
 motion for distant worlds, and explored in so 
 
 'any instances the beauty and wonders of siu% 
 ounding nature, and even attained a degree of 
 /. perfection, the summit of which is concentrated in 
 , may one clay explore itself and its nature? 
 I am convinced it will not. 
 
 To give an account of all the attempts which 
 have been made to explain on this head, what 
 we nevertheless are as ignorant of as before, would 
 be to write a long and useless book; for we 
 have seen nothing but mere speculation, with- 
 
out the least experience for its foundation, and 
 without explaining" satisfactorily a single pheno- 
 menon. 
 
 One conjecture however deserves our notice, 
 since it is deduced from experience in unorga- 
 nised bodies, and might therefore, after previous 
 examination, have been approved or rejected, viz. 
 that the nerves were instruments for an electric 
 process, which determined as well the movement 
 of the body, as the nature of the secretions and 
 re-production of parts. The power of electricity 
 to produce a quick contraction of the muscles, 
 gave occasion to compare it to the operation of 
 the will; and the conclusion drawn from it was/ 
 that the latter was nothing else than an electric 
 discharge between the nerve and the muscular 
 fibres. GAL.VANI, the discoverer of that modifi T 
 cation of electricity, which now bears his name, 
 has more than any other defended this doctrine; 
 but although he has not wanted followers, the in* 
 sufficiency of his hypothesis is now pretty generally 
 acknowledged. THOMAS BTJNZEN, a Dane, laid 
 bare the crural nerve of a frog, and endeavoured 
 to cut it obliquely in such a manner that the me* 
 dulla could be placed in immediate contact with 
 a part of a muscle. He then formed a pile of from 
 
10 
 
 ten to twelve prepared frogs, in the following 
 manner : nerve, muscle, a sponge dipped into a 
 solution of muriate of ammonia, nerve, muscle, 
 &c. and obtained from this pile distinct signs of 
 galvanic action. ^By this he wished to prove, that 
 nerves and muscles may act as electromotors.^ 
 But it is difficult to determine what value such 
 experiments can have in reference to the subject 
 in question ; for it is more than probable, that 
 electricity may be produced here, and act on the 
 expiring life, without its proving that the action 
 of the nervous system of the living animal bore 
 the least analogy to the experiment. Lately, 
 EVERARD HOME has tried to explain the ani- 
 mal secretions, from the changes which the dis- 
 charge of the electric pile produces on liquids ; 
 but, if on the one hand, it be found by future ex- 
 periments, that electricity identifies itself with 
 chemical affinity, and consequently a change of 
 composition is not to be expected without the co- 
 operation of electricity ; yet, on the other hand, 
 the effect of the pile, both on animal and unorga- 
 nic liquids, has nothing at all analogous with the 
 secretions; and by applying this chemical agent 
 to explain the subject, we gain not the least in- 
 formation. 
 
11 
 
 Among those, who have laboured in vain on 
 this field, I ought also to mention the well-known 
 German author, BJEIL. He supposes, that in the 
 nerves there is a matter, analogous to galvanism, 
 which through a kind of electric atmosphere, ope- 
 rates at a small distance, and thereby he has re- 
 vived the idea of an aurea nervea. The manner 
 in which he explains his hypothesis, and the ar- 
 guments he introduces in support of it, constitute 
 an entertaining essay, but does not increase the 
 sum of our real information. 
 
 It is fruitless to expect to obtain any informa- 
 tion on this subject, by any chemical analysis of 
 the matter of the nerves and the brain. Our ex- 
 periments convince us sufficiently, that the ope- 
 ration of the nervous system is not performed by 
 a mutual decomposition of its medulla, and the 
 part on which it operates; for, by tying up any 
 small but essential nerve, we have found, that 
 the greatest disorders have arisen in the oeconomy 
 of the animal, and continued as long as the liga- 
 ture remained, although the nerve below the part 
 tied always retained the same quantity of nervous 
 substance as before. Again, if the ligature is 
 loosened, and the continuity of the medulla re- 
 stored, the disorders will cease. And why is this 
 
continuity so necessary in a channel, the contents 
 of which always remain on the same spot ? It is 
 clear that this indicates an effect by means of 
 transmission, like that of electricity; although, 
 what we hitherto know about electricity, cannot 
 here be applied in explanation. 
 
 In this state of our information, I consider it 
 as no small merit in a lover of the science, if 
 he distinctly lays open what is really known, and 
 determines with equal distinctness, what is yet 
 unknown to us, without filling up the chasm with 
 conjecture. Problematical tenets, they say, are 
 conductors to truth; and I do not altogether 
 deny it, when they are proposed for examination 
 by themselves ; but when in the accumulation of 
 scientific knowledge, they are mixed with the 
 mass of facts, they often lead even the intelligent 
 reader astray, who afterwards cannot, without la- 
 bour and application, get rid of the illusion. Ani- 
 mal Chemistry is more exposed to this intermix- 
 ture of hypothesis than any other science ; partly 
 because much remains still to be explored, and 
 partly because there is still more, which certainly 
 never can be discovered. It might indeed be 
 possible, by applying to this science the many 
 more or less ridiculous medical theories about the 
 
13 
 
 nervous system and the intimate nature of its ope- 
 rations, to compose a whole, which should have a 
 truly scientific appearance ; but all, that in latter 
 times has been tried this way, from what has been 
 called a higher philosophical point of view, has 
 only done honour to the imagination of the au- 
 thor, without bringing the human understanding 
 a hair's-breadth nearer the truth. 
 
 Those of our contemporaries, who have sub- 
 jected parts of the nervous system to chemical 
 experiments, are THOURET, FOURCROY, JOR- 
 DAN, and in some respects, even BICHAT. The 
 former have given us analyses of the matter of the 
 brain, which, considering the time when they were 
 published, are of real merit : they constitute all 
 that Animal Chemistry can yet shew relative to this 
 noble organ ; but in the present state of the ana- 
 lytical part of the science, they need to be revised 
 and corrected. BICHAT has examined the mem- 
 brane of the nerves (the neurilema). He was, 
 properly speakiug, not a Chemist ; but in order to 
 improve his physiological works, he tried on most 
 parts of the animal body the effect of general che- 
 mical agencies, such as that of air, water, alkalies, 
 and mineral acids ; and the experiments thus made 
 on the "neurilema" are all that we know of it 
 
14 
 
 in a chemical sense. The discovery of the pos- 
 sibility of dissolving, by means of caustic alkali, the 
 medullary part of the nerve, so that its membrane 
 should remain as a hollow tube, has afforded a 
 good opportunity for separating the membrane, 
 and has given us some information concerning the 
 nature of the channel which the neurilema forms. 
 
 Next to the nervous system, the principal part 
 in the animal body is acted by the blood and the 
 vessels by which it is circulated. The extremi- 
 ties of these vessels are interwoven with the last 
 ramifications of the nerves, and perform in this 
 union, at the expence of the blood, all the pro- 
 cesses of the animal body. The attention of 
 Chemists was very early directed to the blood ; 
 and its different properties in certain diseases, in- 
 duced them to make several experiments with it. 
 HALES tried to determine the quantity of air 
 which is disengaged in the distillation of the blood. 
 LEMERY and MENGHINI burnt it to ashes, 
 found iron amongst its constituent parts, which 
 the latter even believed himself able to extract 
 from dry blood with the magnet. HOFFMAN 
 examined the different matters which are sepa- 
 rated in the coagulation of blood. LANG RISK, 
 CHEYNE, and SCHWENKE, published for their 
 
15 
 
 time, tolerably explicit analyses of the blood. 
 
 GAUBIUS surpassed them all in accuracy. 
 
 ROUEL.LE, the younger, determined pretty dis- 
 tinctly the salts which are contained in it. HEW- 
 SON described with precision several of the quali- 
 ties of the blood. BUCQUET examined the con- 
 stituent parts of the cruor : and lastly, we have 
 from DEYEUX and PARMENTIER, in answer to 
 a prize-question from the Medical Society at 
 Paris, an explicit analysis of the blood, as well 
 in its healthy state, as in certain diseases. FoUR- 
 CROY and VAUQUELIN added, some years after- 
 wards, an investigation of the colouring matter of 
 the blood ; but all that we have gained, since the 
 excellent work of DEYEUX and PARMENTIER 
 was published, has almost only been the clearing 
 away of some errors, without much positive addi- 
 tional information. I have also attempted to give 
 a detailed analysis of the whole mass of the blood; 
 and, assisted as I have been by the improved state 
 of Chemistry in later times, I may perhaps have 
 succeeded somewhat better than most of my pre- 
 decessors, in tracing the constituent parts of the 
 blood, even such as were unknown to them ; and 
 also in determining in a more decided manner the 
 characters of those that were known ; so that in 
 any future analysis of other humours or parts of 
 
16 
 
 the animal body, they may be ascertained by their 
 chemical properties. Thus, for instance, I have 
 shewn that the fibrin of the colouring matter 
 and the albumen may be combined with mineral 
 acids in excess, and form peculiar and insoluble 
 compounds, but that when the superfluous acid is 
 washed away, they are soluble in water that these 
 matters are easily dissolved in acetic and in phos- 
 phoric acids, and that these acids prevent the co- 
 agulation of the blood, by heat that the fibrin, 
 by being boiled with water, disssolves in a small 
 degree, and that the rest shrinks together, and is 
 insoluble in acetic acid that they all three, by 
 the influence of alcohol and aether, are changed 
 to a certain degree, into peculiar kinds of fat, 
 which, according to the menstruum, have differ- 
 ent pungent smells, and other differences. The 
 ingredients hitherto unknown, which I have 
 found in the blood, are alkaline lactate of pot- 
 ash, and some peculiar animal matters, which in 
 all the humours of the body are found to accom- 
 pany the lactate; and which, in my opinion, 
 owe their existence in the blood to the ab- 
 sorption of those decayed parts of the body, 
 which are destined to be separated by means of 
 secretion. I have also succeeded in correcting 
 several mistakes of my predecessors. It was be- 
 
17 
 
 Ueved from DE HAEN'S statement, that blood 
 contained glue, of that kind which is produced 
 when bones or cartilages are boiled with water ; 
 but I have proved that glue is not found within 
 the animal body, and that DE HAEN, and all 
 after him, have considered as glue, the albumen, 
 in a half coagulated state. Among the imme- 
 diate constituent parts of the blood, some authors 
 have even counted sulphur, because blood, when 
 evaporated in silver vessels, blackens the silver. 
 This conclusion, however, is incorrect, because the 
 sulphur has belonged, as a constituent part, to the 
 albumen, and has been disengaged through the 
 combined destructive effect of boiling, and of the 
 caustic alkali, on the albumen. DEYEUX and 
 PARMENTIER believed that the red colour of 
 the blood was a solution of iron in the free alkali 
 of the blood. FOURCROY and VAUCIUELIN en- 
 deavoured to prove, that it was a solution of red 
 subphosphate of iron* in albumen. They found 
 that albumen, or serum, which was triturated witli 
 this subphosphate before it was dry, dissolved it, 
 and assumed itself a red colour, and that this red 
 colour was still more heightened by caustic alkali. 
 According to these experiments, the colouring of 
 the chyle in the air consisted in the change of the 
 phosphate of iron, from a neutral phosphate of the 
 
 c 
 
18 
 
 the protoxide, to a subphosphate of the peroxide. 
 With the greatest diffidence of myself, I have re- 
 peatedly tried the experiments of those Chemists, 
 the most celebrated of all Europe : and by finding' 
 my results invariably disagree with theirs, I have 
 been compelled to consider their statement as a 
 mistake, and to declare, that, in regard to the 
 manner in which iron is united to the colouring 
 
 o 
 
 matter of the blood, we know as little now, as 
 when iron was first discovered in it- I have en- 
 deavoured to shew, that the colouring matter, 
 much as it resembles albumen, cannot itself be 
 albumen; and that as LEEUWENHOEK and 
 HARTSOEKER proved long ago, by microscopical 
 observations, it is not dissolved in the blood, but 
 floats in it in a suspended state ; for if the coagu- 
 lated cruor is triturated in serum, part of the co- 
 louring matter is thereby separated, and the se- 
 rum assumes a red colour ; but if it is suffered 
 to settle in a cylindrical glass, the colouring 
 matter slowly precipitates itself to the bottom, 
 and the serum above becomes clear, as before. 
 
 I have proved, that metallic oxides, particu- 
 larly those of iron, may, in a certain degree, be 
 dissolved by the serum, and thereby, more or less, 
 Change its colour; but that none of them imparts 
 
19 
 
 to it the colour of blood, and that the serum, thus 
 impregnated with iron, is entirely destitute of the 
 intrinsic characters of the colouring* matter. As 
 none of our most delicate tests of iron discover 
 its presence in the colouring matter, I thought 
 myself entitled to conclude, that iron cannot 
 be found in it in a saline form ; ancl, as we find 
 it impossible, even with the strongest acids, to 
 extract from the blood, or from its charcoal, 
 either the iron or the earthy phosphate, which are 
 so abundantly contained in the ashes of blood, 
 it follows of course, that neither of these sub- 
 stances exists there in the state of a salt ; from 
 which it is very probable, that blood contains the 
 elements of these salts, united in a manner different 
 from their combination in the salts. From this 
 circumstance, I further concluded, that the sub- 
 phosphate, or bone earth, which was supposed to 
 be contained in the blood, did really not exist 
 there, for I found that it could not be extracted 
 from dried blood with any diluted acid ; on the 
 contrary, that bone earth must always be a pro- 
 duction of the decomposition of the immediate 
 constituent parts of the blood, and that it is gene- 
 rated just on the very spot where its presence is 
 required. 
 
 c 2 
 
20 
 
 On the cauSe of the coagulation of the fibrin 
 out of the body, many experiments have been 
 made. Blood has been carefully kept at the 
 same temperature, and exposed to air containing 
 no oxygen gas, and alsb in an exhausted receiver- 
 Blood has been frozen rapidly, and again thawed, 
 Or mixed with water ; but, in all these expe- 
 riments, it has, sooner or later, coagulated. The 
 cause of this coagulation remains entirely un- 
 known to us; and a conjecture has been made, 
 that it is only its motion in the vessels which pre- 
 vents it. Some Experimenters have ascribed to 
 the fibrin a vital irritability, in consequence of 
 the tremulous motion perceivable in small drops 
 of blood, when exposed to the effect of the elec- 
 tric column ; but this idea was proved by HEID- 
 MAN to be completely erroneous, and he shewed 
 that the motion proceeded from the shrinking of 
 the fibrin itself, when suddenly coagulated. The 
 chemical examination of the fibrin, the colour- 
 ing matter, and the albumen, lias discovered that 
 these three substances very nearly resemb}e one 
 another in chemical properties ; their composition 
 must therefore be nearly similar, and they are 
 capable either of being changed, by means of 
 small alterations within the living animal, the 
 
 <*ne into the other, or of being employed to 
 
 " 
 
21 
 
 produce the same substances in the excretions, 
 or in the r^-produetion of solid parts, instead of 
 those which are decayed, or worn out. 
 
 On accurately comparing human blood with 
 that of a bullock, I have found an astonishing 
 resemblance between the two. The same spe- 
 cific constituent parts in both, the same propoi%- 
 tions, and nearly the same chemical characters, 
 make it easy to explain the successful results of 
 several experiments that have been made, to 
 transfuse the blood of herbivorous animals into 
 human bodies, from which the blood had been 
 drawn at the time. I observed, however, a re- 
 markable difference in certain characters of the 
 constituents of the blood in man, from what I 
 found in that of the bnllock. The fibrin, as well 
 as the colouring matter, and the albumen, from 
 human blood, after they are dried, are much 
 more easily burnt to ashes ; and the charred hu- 
 man blood requires neither so strong, nor so pro- 
 tracted a heat, to be entirely reduced to ashes, 
 as that of the bullock. This difference in the fa- 
 cility of burning, indicates clearly a greater pro- 
 portion of nitrogene in the constituent parts of the 
 bullock's blood, which is still more clearly proVed 
 by the circumstance, that the charcoal of the 
 
22 
 
 blood of the bullock, when burnt slowly, con- 
 stantly gives off carbonat of ammonia, although 
 it has been heated in an open vessel, and freely 
 exposed to the air. This indication of a greater 
 quantity of nitrogen e in the constituent parts of 
 the bodies of herbivorous animals, than in those 
 of the human body, is the more unexpected, as 
 the food of man, in general, contains more nitro- 
 gene ; whereas, on the contrary, nitrogene, which 
 has hitherto been considered as an elementary 
 body, is found but in small proportions in those 
 vegetables, which constitute the foorl of the bul- 
 lock. Our information on this subject will pro- 
 bably be considerably increased, by an examina-* 
 tion of the so much contested nature of nitro- 
 gene, 
 
 The blood separates itself at the finest ramifi- 
 cations of the arteries, into a coloured portion, 
 which returns the suspended particles of the co- 
 louring matter through the veins, and a colour- 
 less portion, which penetrates the finest ramifi- 
 cations. These ultimate ramifications of the ar- 
 teries, we call, after BICHAT, capillary vessels. 
 The colouring matter changes, on this occasion, 
 its colour, and turns dark brown, or blackish ; 
 but it is entirely unknown to us what influence 
 
23 
 
 this changing of colour may produce on the co- 
 lourless fluid, which is conveyed by the capillary 
 vessels. As the colouring- matter is not dissolved, 
 but only mechanically mixed with the blood, we 
 may consider the separation of the arterial blood 
 into coloured and uncoloured, as a process of fil- 
 tration, which only admits the colouring matter 
 to penetrate into the veins, while, on the other 
 hand, the serum alone is forced into the finest 
 channels, 
 
 It would be of the greatest importance to Ani- 
 mal Chemistry, to examine the serum, in the 
 state in which it penetrates the capillary vessels ; 
 but I cannot conceive how it would be possible 
 to collect it, even in a very small quantity. It 
 is probable, that this humour is the common se- 
 rum, which also contains dissolved fibrin; and if 
 this supposition be correct, it follows, that the 
 fibrin within the vessels must also be dissolved in 
 the serum, and not belong to the suspended co- 
 louring matter. Such I have always considered 
 the composition of the blood ; but, except the 
 confirmation we receive, by examining the humour 
 of the absorbing vessels, I have not been able to 
 discover any experiment to confirm, or refute, 
 this supposition. 
 
24 
 
 The blood vessels have, as yet, been but little 
 examined as to their chemical properties; and, 
 with the exception of Bi CHAT'S experiment of 
 macerating their various membranes, we have 
 no investigation on the subject. The fibrous 
 membrane of the arteries, which, unquestionably, 
 is the most remarkable of all, has long been 
 considered as composed of annular muscles. 
 This was the opinion of HALLE R, and on this 
 supposition he has founded his theory of tliefmlse, 
 which to this day is adopted in all our elementary 
 books. JOHN HUNTER disapproved HAULER'S 
 idea of the muscular action of the arteries, as 
 being the cause of their pulsation. BICHAT tried 
 to irritate the arteries of living animals, with 
 such chemical and mechanical stimuli as affect 
 the muscular fibre, but without being able to ex- 
 cite the least perceptible change in their motion ; 
 and he declared, in consequence of these experi- 
 ments, that the pulsation originated only in that 
 of the heart; that it did not consist in dilatation, 
 but was only a motion from its former place, or, 
 as he himself called it, a locomotion. The che- 
 mical examination of the fibrous membrane of 
 the arteries, now became of peculiar consequence, 
 as the only possible means to decide how far the 
 fibre of the artery was of the same nature as that 
 
of the muscle. I undertook this examination, 
 and obtained very satisfactory . and decisive re- 
 sults. In consequence of the experiments thus 
 made, it is beyond all doubt, that the fibrous 
 membrane of the arteries cannot be a muscle ; for 
 while the latter is soft and flaccid, and contains 
 more than three-fourths of its weight of water, 
 the artery is dry and very elastic; the muscular 
 fibre possesses the same chemical properties as 
 the fibrin of the blood ; for instance, that of be- 
 ing soluble in acetic acid, and of forming scarcely 
 soluble compounds with sulphuric, nitric, and 
 muriatic acids; but the arterial fibre has altoge- 
 ther opposite qualities, viz. that of not being so- 
 i^ble in acetic acid, but pretty easily soluble in 
 
 miveral acids, diluted with water to a certain 
 \ 
 
 degree, from which solution it cannot be preci- 
 pitated by means of alkali, or alkaline prussiats, 
 which are the tests for the acid solution of fibrin, 
 &c. Consequently, as the arterial fibre neither 
 has the structure of a muscle, nor its chemical 
 properties and composition, it cannot be a muscle, 
 nor perform the functions of a muscle, which is, 
 besides, sufficiently evident from its elasticity. 
 This elasticity in the arteries, however, compen- 
 sates fully the muscular power. HALLER'S de- 
 scription of the pulse, is of course correct, not* 
 
withstanding his opinion on the cause of the ar- 
 terial contraction, has been proved to be incor- 
 rect. BICHAT'S idea, on the contrary, that the 
 pulse did not consist in a dilatation of the arteries, 
 but only in a locomotion, occasioned by their nu- 
 merous inflections, when the heart presses the 
 blood, cannot but be incorrect, since it is contrary 
 to the laws of hydrostatics. 
 
 As chemical analysis has sufficiently proved 
 that the fibrous membrane of the arteries is not a 
 muscle, and, consequently, cannot exhibit a spon- 
 taneous contraction; and, as we clearly perceive * 
 from its elasticity, that it must be dilated during 
 the systole of the heart, and resume its original size 
 during the diastole; it follows, that the quickness 
 of the pulse in the same individual, can never vary 
 in different parts of the body. All other dispari- 
 ties, except this, may be possible. 
 
 Several medical authors have related cases, 
 where this unequal velocity is said to have been 
 observed; but we must consider these observa- 
 tions as mistakes, after we have seen the impos- 
 sibility of the existence of such cases. A deci- 
 sion of this long-contested question is of the 
 greatest consequence to the Medical Science* 
 
21 
 
 since it convinces us that spasms cannot exist in 
 the greater arteries, and that all the aberrations 
 in the circulation of the blood, generally ascribed 
 to this cause, altogether relate to the unquestion- 
 ably muscular heart, with its auricles, and in 
 some degree to the muscular fibres, which sur- 
 round the extremities of the venae cavse. 
 
 I mentioned, that the final ramifications of 
 arteries, on account of their fineness, are called 
 capillary vessels. The anatomy of these vessels 
 is almost unknown, and the manner in which 
 they terminate is a complete secret. It has hi- 
 therto been impossible to institute any chemical 
 analysis of their integuments, as they cannot be 
 separated from those parts with which they are 
 interwoven. These vessels, in all probability, have 
 a peculiar power slowly to carry forwards the 
 humours contained in them; but the mechanism 
 of this process will probably long remain a se- 
 cret. It is in these vessels that the inexplicable 
 processes of secretion and re-production of solids 
 is performed by means of the co-operation of the 
 nerves. The same nature, which is incompre- 
 hensible to us, when extended to immensity, es- 
 capes no less our penetration, when contracted 
 jnto too narrow limits. At both these extremi- 
 
28 
 
 ties a boundary is set to our experience, which 
 succeeding- ages may extend, without ever being' 
 able to comprehend the whole. 
 
 The process, which in respiration changes the 
 dark venous blood into crimson coloured blood, 
 was first examined by CIGNA, and not without 
 success ; and after our great SCHEELE had taught 
 us the composition of the atmospheric air, and de- 
 monstrated as well the necessity of one of its consti- 
 tuents for the support of life, as the insufficiency of 
 the other, the change of the air in the lungs was 
 explained by LAVOISIER, MENZIES, and GOOD- 
 WYN, in a very satisfactory manner. They found, 
 that oxygen gas was consumed, and that its place 
 was filled up by carbonic acid gas ; as also, that 
 the expired air contained a very considerable 
 quantity of aqueous vapour. From this circum- 
 stance, LAVOISIER concluded, that the dark ve- 
 nous blood contained a combination of carbon 
 and hydrogene, which imparted to it the dark 
 colour ; and which, when exposed to air, became 
 oxygenized, and formed carbonic acid and water f 
 whereby part of the water, which accompanies 
 the expired air, was produced ; while the other 
 part evaporated from the humid membrane of 
 
29 
 
 the lung-s. He endeavoured to state the quan- 
 tities of these productions ; but the numbers he 
 has given us exceed, in some degree, the due me- 
 ilium, because, in his days, the quantity of oxy- 
 gene in the air was taken to be greater than it 
 really is, by which means his eudiometric expe- 
 riments could not be sufficiently accurate. He 
 found further, that no nitrogene was absorbed by 
 the blood. 
 
 Experiments were now made w r ith other kinds 
 of air, besides the atmospheric ; and among the 
 many, who have laboured in this field, Dr. BED- 
 DOES has particularly distinguished himself. He 
 tried to cure certain diseases, by means of inha- 
 lation, and gave us several instances of apparently 
 successful results. However, a multiplied experi- 
 ence has shewn, that less has been gained from 
 these inhalations than was originally believed. 
 As a concomitant result from these experiments it 
 was found, that hydrogene, as well as nitrogene, 
 might be inhaled without any deleterious effect in 
 the beginning ; and that the respiration of hydro- 
 gene gas produced a cheering effect, somewhat 
 like that of spirituous liquors. It was, however, 
 requisite that both these gases should be in a pure 
 state. All other kinds of gases were found to be 
 
30 
 
 noxious, and even destructive. BEDDOES cm- 
 ployed in his experiments HUMPHRY DAVY, a 
 young man of promising genius, who has since far 
 surpassed his instructor in celebrity and merit. DA- 
 VY discovered the intoxicating* power of the nitrous 
 oxyd gas, and shewed, that it was absorbed, during 
 respiration, by the blood, to which it imparts a 
 purple colour, and extricates from it part of the 
 gases it had formerly absorbed. He afterwards 
 extended his experiments to respiration in atmos- 
 pheric air ; and it appeared to him, that the blood 
 actually absorbed part of the nitrogene in the air, 
 so that about three or four cubic inches were ab- 
 sorbed every minute. HENDERSON and PFAFF 
 repeated his experiments with similar results ; & 
 mistake, however, has since been discovered in 
 these experiments, in consequence of not being ac- 
 quainted with the laws, which regulate the mix- 
 ture of gases with liquids. About this time, how- 
 ever, they were discovered by JOHN D ALT ON, 
 an ingenuous natural philosopher, who soon after- 
 wards published his experiments. One of these 
 rules is, that, when a liquid comes in contact with 
 a gas, it absorbs a determined proportion of the 
 gas ; and if it then comes in contact with another 
 gas, it absorbs also a quantity of that, but emits, 
 at the same time, a part of what it had absorbed 
 
31 
 
 before, till the gas over the liquid, and the part 
 absorbed by it, arrive at a certain degree of aequi- 
 libriunu As in all these experiments, the very 
 same respired air was constantly inhaled, it fol- 
 lows, that the relative quantity of nitrogene in the 
 air must have been increased, and thereby pro- 
 duced a double cause of mistakes, partly from the 
 gas, remaining in the 1 tings, containing more ni- 
 trogene ; and partly, from the circumstance, that 
 in proportion as the air in the lungs near the blood 
 contained more nitrogene, the blood itself, or ra- 
 ther the water in the blood, must absorb a new 
 quantity of nitrogene gas, in order to approxi- 
 mate to perfect saturation with this gas ; just as, 
 on the other hand, the blood, during the respira- 
 tion of gases, that contain no nitrogene, must con- 
 tinually return part of the nitrogene, which it had 
 absorbed before, which circumstance experience 
 has also fully confirmed. The cause of this mis- 
 take, therefore, did not originate in ah incorrect 
 or hasty experiment, but was the necessary 
 consequence of the state of the science at the 
 time. The experiments on respiration were last- 
 ly repeated by two English Chemists, ALLEN* 
 and PEPYS, on a larger scale, and with a preci- 
 sion, which far surpassed all examinations hither- 
 to made. In these experiments they had tlie 
 
opportunity of using the excellent large gasome* 
 ters of the Royal Institution in London ; and the 
 principal result of them was, that the volume of 
 the air, during the respiration, is so inconsidera- 
 bly diminished, that the real absorption hardly 
 amounts to more than two thirds per cent, of its 
 volume. On the other hand they found, that the 
 carbonic acid gas, just produced, fills precisely 
 the room of the consumed oxygene g*as. As it 
 was known already, that oxygene gas, during its 
 transformation into carbonic acid gas, does not 
 alter its volume, and that consequently 100 cubic 
 inches of oxygene gas, in which carbon had been, 
 burnt, produces exactly 100 c. i. of carbonic acid 
 gas, it was completely proved by ALLEN and 
 PEPYS'S experiments, that no hydrogene is oxy- 
 dated in the lungs that the oxygene is consumed 
 only by the charcoal -and that, for the rest, the 
 blood, according to all appearance > is not oxy- 
 dated, but only emits carbon, (or is decar- 
 bonized). 
 
 These chemists could not observe any other 
 alterations in the composition of the expired air : 
 it had lost no nitrogene, and acquired no other 
 aerial substance, than carbonic acid gas. This 
 constituted about 8 p. c. of the volume of the 
 
33 
 
 air, which was increased to 10 p. c. if the same 
 air was repeatedly respired ; but it never ex- 
 ceeded this quantity however long the respiration 
 of the same air was continued* Again, on those 
 occasions, where the respiration was performed 
 \vith some difficulty, more oxygene was absorbed, 
 than carbonic acid gas produced. These Gentle- 
 men had the kindness to send me a copy of their 
 essay, inserted in thePhilosophical Transactions for 
 1808; in consequence of which, I took the liberty 
 to propose to them some farther experiments ; for 
 although it was easy to explain the loss of nitro- 
 gen e gas in DAVY'S experiments, and there was 
 consequently no reason to doubt the correctness 
 of their observation, that no nitrogene disappears 
 during respiration, yet I had, for some time 
 back, entertained the idea, that nitrogene might 
 possibly be absorbed by the blood of herbivorous 
 animals, whereby their bodies became provided 
 with the nitrogene, which was wanting in their 
 food, and I therefore proposed to Messrs. ALLEN 
 and PEPYS to examine also the respiration of 
 herbivorous animals, with respect to the absorption 
 of the nitrogene. They executed this experiment, 
 and obtained altogether unexpected results. They 
 made use of guinea pigs, which were placed in a 
 gasometer, and kept there for about an hour, 
 
 D 
 
34 
 
 after which, the air was examined. When nsing r 
 atmospheric air, they found the quantity of nitro- 
 gene gas entirely undiminished, and the consumed 
 oxygen gas compensated by carbonic acid gas, 
 just as in man. They then caused these animals 
 to respire pure oxygene gas, in an apparatus, so 
 constructed, that the respired gas could be ex- 
 changed for new, and that, in which the animal 
 had respired, be separated for examination. 
 This was found to contain a large proportion of 
 nitrogene gas, which, however, was decreased 
 more and more in the succeeding portions, They 
 now mixed 78 parts of pure hydrogene gas with 
 22 parts of oxygene gas; and in this artificial 
 atmosphere, they confined a guinea pig for an 
 hour, having previously ascertained the volume 
 with minute exactness, and the same result was 
 again obtained: the expired air was mixed with 
 nitrogene gas, in a decreasing proportion ; but, 
 the quantity of nitrogene gas, obtained in this 
 manner, exceeded, in some experiments, the bulk 
 of the animal. They found, besides this, that 
 the animals, after the lapse of an hour, became 
 sleepy, without any perceptible sign of illness; 
 and that, during this period, less carbonic acid 
 gas was produced. As in these experiments, more 
 aitrogene gas was exhaled, than the fluids of the 
 
35 
 
 animal, at the moment of its introduction into tha 
 mixed gas, could possibly contain, in the state of 
 absorbed nitrogene gas, it appears;, that, after 
 the absorbed nitrogene gas was exhaled from the 
 blood, according to the above-mentioned law, for 
 the combination of mixed gases with liquids, a 
 fresh quantity of nitrogene gas was supplied at the' 
 expence of the constituent parts of the blood, 
 which seems to have a constant tendency to pro- 
 vide itself with nitrogene gas ; and this must again 
 be exhaled, in order to divide itself between the 
 blood and the gas in the lungs. Should this con- 
 jecture be supported by future observations, it 
 will, nevertheless, always be looked upon as a 
 peculiar and uncommon chemical process, that 
 nitrogene gas should be disengaged without any 
 particular change in the composition of the blood, 
 when we consider, that nitrogene is in general " 
 disengaged only by operations more or less de- 
 structive, such as, for instance, by the effect of 
 mineral acids. 
 
 This is at present the extent of our information 
 about the change of the air by respiration. The 
 influence which the air exercises on the blood, 
 and the changes which are thereby produced in 
 the composition of the blood, are, as yet un- 
 XI 2 
 
30 
 
 known. We have only been able to ascertain, 
 that the dark blood turns red ; and we conclude, 
 from the quality of the respired air, that the dark 
 blood has lost a portion of its carborv ; but whether 
 any of the immediate constituent parts of the 
 blood have become altered in their qualities, is a 
 subject not yet examined, although it is probable, 
 that, by a chemical analysis, very interesting- re- 
 sults might be derived from the comparison be- 
 tween venous and arterial bk>od. It has been ge- 
 nerally believed, that every part of the blood is 
 influenced by the air; that it absorbs oxygene,, 
 and exhales carbonic acid gas ; but this is not the 
 case* Bloody in which the colouring* matter is 
 still contained, absorbs oxygene gas very quickly,, 
 when out of the body and shaken in atmospheric 
 air; it also- retains at the sam-e time some p&rt of 
 the carbonic acid, thereby produced ; on the other 
 hand, serum, when destitute of colouring matter, 
 does not change the atmospheric air before it be- 
 gins to putrify. 
 
 The principal effect on the air is produced by 
 the colouring matter, and as this matter does not 
 penetrate any of the re-producing, and but few 
 of the secreting capillary vessels, it appears as if 
 the principal object of the colouring matter, were 
 
37 
 
 f,lie production of animal heat. CRAWFORD sta- 
 ted, in consequence of his experiments, that arte- 
 rial blood was possessed of a greater specific heat 
 than the venous, in the proportion of 115 to 100. 
 Taking this statement for granted, it follows, 
 that when the venous blood turns red in the lungs, 
 it must be cooled about 5 degrees, in case it be 
 not heated by the very process which renders it 
 arterial. The ideas, about the distribution of 
 heat, through the body, were at first very vague, 
 and the lungs were considered as a stove, in 
 which the heat was disengaged, and afterwards 
 carried with the blood to all parts of the body. 
 According to CRAWFORD'S idea, it seems as 
 if the arterial blood, in order to maintain the 
 same temperature, as when venous, did exactly 
 want that quantity of heat, vhich is engaged from 
 the air, by the oxygene gas being changed into 
 carbonic acid gas; and when the arterial blood 
 again becomes venous in every part of the body, 
 the retained heat becomes disengaged, and restores 
 what has been Jost by means of transpiration, 
 and by the access of the ambient air, whereby 
 the body always preserves the same degree of 
 heat. If the colouring matter is the principal 
 cause of this, it is easy to perceive, wherefore 
 the body, after abundant losses of blood, is more 
 
 3 
 
cold; and wherefore bleeding 1 , even in asthenic 
 fevers, lessens the violence of the disease. On 
 these occasions, the effect cannot be owing to the 
 diminished bulk of the humours alone, since the 
 former diameter of the vessels is soon restored by 
 the absorption of new fluids, from the alimentary 
 canal; but the diminution of the colouring" matter 
 of the blood, and the production of heat, which 
 depends on it, must also have a considerable share 
 in it. Practitioners in physic will, no doubt, re- 
 collect circumstances in the course of their expe- 
 rience, which will give still greater probability 
 to this idea, 
 
 By ascertaining the quantity of carbonic acid, 
 which is daily formed by respiration, we may 
 pretty nearly determine the quantity of heat, 
 which is necessary for maintaining the equable 
 temperature of the body. ALLEN and PEPYS 
 found, that a middle-sized person expires in 24 
 hours, 39,534 cubic inches of carbonic acid gas, 
 which, when weighed, makes 19,683 grains, or 39 
 ounces of carbonic acid. These contain 11 ounces 
 1 dram of carbon ; from which it follows, that a 
 middle-sized person wants, within 24 hours, as 
 much heat for keeping the body at -f- 32 * a 
 
 * The Author uses the centigrade thermometer, 
 
39 
 
 a pound of 'charcoal would disengage during its 
 combustion. It ought also to be observed, that 
 the carbon in the blood, as being in a liquid state, 
 may possibly produce more heat from its combus- 
 tion, than when in its solid state. AH these cal- 
 culations, however, have so little claim to be re- 
 garded as exact, that they, are made rather with 
 a view to approximate to the truth, than to be 
 rjelied upon as accurate. For my part, I must 
 confess, that if the observations of ALLEN and 
 PEPYS be correct, it will be very difficult to con- 
 ceive how the body can compensate the extraor- 
 dinary consumption of carbon, which, besides 
 what is separated in other places, presupposes at 
 least from 8 to 10 pounds weight of food within 
 the day, which is more, by far, than any person 
 generally consumes. 
 
 Although the changes, which the blood, during 
 respiration, undergoes in the lungs, according to 
 all appearance, resemble those, which are pro- 
 duced in the blood by the air out of the body ; an 
 influence, in this process, has also been ascribed 
 to the nervous, system, without which, it could 
 not take place. DUPUYTREN, in an experi- 
 ment on horses and dogs, divided the eighth 
 
 air , of nerves, near the oesophagus, and 
 
40 
 
 served, that the animal, though respiration wa* 
 complete, died within a short time for want of 
 oxidation. If an artery was opened, and the 
 nerve afterwards divided on one side, the blood, 
 which issued from the artery, assumed for a few 
 moments a darker colour, but was again reddened* 
 If the nerve was divided on both sides, the blood 
 which flowed from the artery became venous, and 
 the animal died, the fine epidermis on the inte^ 
 rior side of the nose and mouth becoming black- 
 ened. Again, if instead of this, he only com- 
 pressed the nerves, the arterial blood became 
 dark, and continued in that state as long as the 
 compression lasted, but assumed again a crimson 
 colour as soon as the compression ceased. These 
 experiments prove, in a decided manner, the in- 
 fluence of the nerves upon the change of the 
 blood in the lungs, if they were but correctly per- 
 formed and related. In the mean time, it is well 
 known that BAGLIVI and BICHAT have made 
 similar experiments, and drawn from them quite 
 different results. Besides this, one of DUPUY- 
 TREN'S countrymen, DUCROTAY DE BLAIN- 
 VH,LE, has repeated his experiments, and found 
 that the animal indeed, dies sometime after the 
 eighth pair of the nerves have been divided, but 
 Jfrom quite another cause than the cessation, of 
 
41 
 
 the change in the blood during respiration. This 
 was afterwards still further examined by EM- 
 MERT, with all the accuracy we could wish ift 
 a skilful experimenter, and he has satisfactorily 
 proved, that the dividing of the eighth pair of 
 nerves has no immediate influence on the change 
 of the blood in the lungs, but that it affects the 
 respiration, which, by degrees, becomes more 
 and more uneasy ; after which, the blood in the 
 arteries begins to become dark, so that, when 
 the animal, after several hours, dies, it is found 
 to have venous blood in the arteries, because the 
 respiration has ceased, 
 
 Of the difference in the blood in different ages, 
 and during different diseases, we know hardly 
 any thing. It has been supposed, that the blood 
 of the foetus underwent, in the placenta, a pro- 
 cess not unlike that, which takes place in the 
 lungs after birth, and that it was returned through 
 the veins of the navel-string; but credible authors 
 have asserted, that the eye cannot distinguish be- 
 tween the arterial and venous blood of the foetus. 
 The chief object of the process in the lungs, is 
 the maintaining of the animal heat, but the foetus 
 derives its temperature from the surrounding me- 
 dium, and consequently wants no source of heat 
 
42 
 
 of its own ; it would, on the contrary, by such a 
 source, be constantly kept at a much higher tem- 
 perature, than the mammalia in general have. 
 This circumstance is, of course, decisive against 
 the change of the colouring matter in the placenta, 
 although we must confess, that the stay of the 
 blood there must answer some important purpose. 
 FOURCROY has communicated some observa- 
 tions on the blood of the foetus; but they seem 
 to bave been made by chance, and not to be de- 
 duced from any experiments, 
 
 - * ' -_ , f " * 
 
 The dissimilarity of the blood in certain diseases 
 was examined by DEYJEUX and PARMENTIER, 
 and the result of their examination was, that the 
 difference from the healthy state was so inconsi- 
 derable, that in the state of the science at that 
 time, they were hardly to be ascertained. Du-r 
 PUYTREN, THENARB and NICOLAS, have made 
 experiments with diabetic blood, and proved, 
 that not the smallest portion of the sugar, which 
 is so abundantly found in the urine of those afr 
 flicted with diabetes, can be discovered in the 
 blood. 
 
 What I have here stated concerning the blood 
 and respiration, relates chiefly to man. We have 
 
43 
 
 no comparative experiments on the blood of the. 
 brute creation; and of this, Animal Chemistry 
 has taught us nothing beyond the external cha- 
 racters, which, in Zoology, constitute a part of 
 the distinctions of the different classes of animals. 
 On the respiration of birds, and amphibia, no 
 experiments have been made. We only know, 
 that, birds are exceedingly delicate as to air, 
 and that in the same atmosphere in which a bird 
 dies, a mouse may live without any perceptible 
 inconvenience. On the respiration of fishes, we 
 are furnished with more experiments. It is cer- 
 tain, that the fish oxidates its blood in the gills, 
 at the expence of the oxygene gas, which the 
 water contains to the amount of about TOT? of its 
 volume. But this kind of respiration is not of so 
 much consequence to fish, as to the mammalia, 
 since fishes may continue alive for several days 
 in water, which is void of ^air; but they die at 
 last, if air is not admitted, and it cannot be ob- 
 served, that the least decomposition of the water 
 takes place by their respiration. Fishes have a 
 vessel, which is called the air bladder, and which 
 has, though probably not correctly, been consi- 
 dered as partaking in the operations of the gills 
 on the blood, whereas it seems intended to regu- 
 late the specific weight of fish, so that it may, 
 
44 
 
 5* ithout difficulty, rise of* sink in the water. In 
 fresh water fish, this bladder contains, according 1 
 to ERMAN T S experiment, nitrogene gas, mixed 
 with varying portions of oxygene gas, which is, 
 however, never found in it in the same propor- 
 tion as in atmospheric air. BIOT found, on the 
 contrary, that in salt-water fish it contained oxy- 
 gene gas, increasing in proportion as the fish was 
 in the habit of living at a greater depth, so that 
 in fishes, which were caught in water 1000 me] 
 tres deep, the air contained from 1 to TO of oxy- 
 gene gas. In the bladder of such fish, the air is 
 so compressed by the heavy column of water 
 above, that when the fish is drawn up, the bladder 
 swells and forces the stomach through the mouth. 
 
 o 
 
 In one kind of fish, the colitis fossilis, EKMAN 
 observed a doub ] respiration. Ii: water, con- 
 taining air, the fisti breathed as usual, through 
 its gills -, but if the water was deprived of its por- 
 tion of oxygene gas, the fish rose above the smv 
 face, drew air through its mouth and swallowed 
 it. This air penetrated tjie intestines, the blood 
 vessels of which were reddened, and when it had 
 lost its portion of oxygene gas, the fish discharged 
 }t by the rectum. 
 
 The respiration of insects was very carefully 
 
45 
 
 examined by HAUSSMAN, who found, that they 
 absorbed oxygene gas and returned carbonic 
 acid. He even examined the respiration of some 
 worms, and perceived, that they also changed 
 oxygene gas into carbonic acid. SPALLANZANI 
 had observed the same long before, but he also 
 believed that several of the mollusca absorbed 
 nitrogene gas, a circumstance, which we must 
 call in question, till it is confirmed or rejected 
 by further chemical experiments. 
 
 I have already remarked, that that portion of 
 the blood, which goes to the reproduction of the 
 various parts of the body, is void of colouring 
 matter, and penetrates the last fine ramifications 
 of the arteries, from whence it cannot afterwards 
 be returned, but must exude through the open- 
 ings of the capillary vessels. Just at this point 
 those parts are generated, which are to be repro- 
 duced, whereupon the remaining part is either 
 absorbed by a particular system of vessels-, which 
 from their functions bear the name of absor- 
 bents, or discharged by means of secretions and 
 excretions. These vessels are placed in all part* 
 of the body with their absorbing extremities 
 open, and take up not only the remainder of the 
 imcoloured blood after the reproduction, but also 
 
46 
 
 those parts, which have been destroyed in exe* 
 cuting their respective functions, and they con- 
 duct from the intestines the matters prepared 
 there for the regeneration of blood, These ves- 
 sels, which are so very important, when we con* 
 sider their functions, are extremely small, and for 
 that reason very difficult to examine in an ana- 
 tomical, and still more in a chemical sense ; con- 
 sequently we have no certain knowledge of their 
 composition, nor of the mechanical process, 
 whereby the humours are conveyed through 
 them. Their own humour, the lymph, varying 
 in its modifications according to the place, from 
 which it has been extracted, is also but little 
 known. We have hitherto only a single ana- 
 lysis of it, which however, affords us considera- 
 ble information. It was instituted by EMMERT 
 and REUSS, and the result of it was, that the 
 lymph resembles serum in its appearance, and, 
 when observed with a compound microscope, is 
 perceived to be a complete chemical solution ; 
 but it thickens after some time, and becomes a 
 coagulum, which is altogether like the fibrin of 
 the blood. This humour consequently contains 
 dissolved fibrin, from which We further iiifeiy 
 that the serum, which penetrates the reproduc ing- 
 capillary vessels, must also contain it, and that. 
 
47 
 
 if the fibrin is here coagulated from a complete 
 solution, the same must be the case in the blood* 
 
 It would be of the greatest consequence to ani- 
 mal chemistry, were we able to- make a compa- 
 rison between the humour in the capillary vessels 
 before the secretion, and the same humour after it 
 
 '. ' -' 4 
 
 has been taken up by the absorbents. There is no 
 doubt but that we should find differences accord- 
 ing to the dissimilarity of what has been secreted 
 or reproduced. Another circumstance of great 
 moment, which is wanting* in the examination of 
 the fluid in the absorbents, is to know the nature 
 of the decayed and useless parts, which have been 
 absorbed by these vessels, and can only be car- 
 ried off in that way. The examination of the 
 humours in the muscles, and of the urine, gives me 
 reason to suppose, that most matters are changed 
 into lactic acid, phosphoric acid, and the other 
 animal matters, which are soluble in water and 
 spirits, and which accompany the lactates in the 
 humours of the body, and constitute the syrupy 
 extract, which is obtained in their analysis. If 
 this be the case, the humours of the absorbent s, 
 after the coagulation of the albumen by boil- 
 ing and evaporation of the w r ater, must leave 
 
48 
 
 a far greater quantity of the syrupy extract than 
 the serum. That part of the humours of the ca- 
 pillary vessels, which is not intended to be 
 brought back into the blood, is carried off through 
 those organs called secretory and excretory. The 
 fresh humours, which are formed in these organs 
 from the constituent part of the blood> are fre^ 
 quently of the most different character ; but, 
 in comparing them more accurately with each 
 other, I have found, that they all have their own 
 characteristic constituents, among which the 
 greater part still retain some of the characters of 
 the albumen and the fibrin, from which they are 
 produced. I have given them names according to 
 the humours in which they appear* as bilious mat- 
 ter, lacrymal matter, fyc. The humour, in which 
 these characteristic constituents are found to be 
 dissolved, contains the salts of the blood, and of- 
 ten its alkali, in the same quantity as in the blood. 
 Some of the secreted humours are equally con- 
 centrated with the blood, as for instance, the bile; 
 others again are more aqueous, but none are more 
 concentrated than the blood. The secretions, or 
 such humours, as before their discharge are in- 
 tended to be used for some purpose within the 
 body, are alkaline ; the excretions, on the other 
 
49 
 
 hand, or such as are to be thrown off immediately 
 are all acid, for instance, sweat, urine, milk, and 
 the free acid which they contain is lactic. 
 
 What I have hitherto remarked, constitutes 
 the sum of our knowledge relative to the two 
 systems, on which animal life principally de- 
 pends, viz. the nerves and blood vessels. Through 
 these, the other branches of the body execute the 
 various operations, for which they are destined. 
 They consequently escape our notice as to thd 
 manner in which they perform their functions ; 
 our examinations are therefore limited to what 
 they perform. 
 
 The internal parts of the body lie closely joined 
 to each other, leaving only small interstices, filled 
 with a peculiar matter, which, from its struc- 
 ture has obtained the name of cellular texture. 
 To form to ourselves some idea of this matter, 
 we may consider it as an intervening medium, 
 intended to prevent any one space from being 
 empty. This cellular texture consequently ex- 
 tends itself over the whole body, and is met with 
 in all its parts, connecting itself with the interior 
 parts of several of them, as for instance, with the 
 muscles. Its composition has been but imper* 
 
 E 
 
50 
 
 fectly examined, and what we know about it is not 
 the fruit of a direct investigation, but a collection 
 of accidental observations, and from these we have 
 learned, that the cellular texture, when boiled 
 slowly, is dissolved by degrees in great mea- 
 sure, and that the solution, whilst cooling, co- 
 agulates to a jelly and contains glue. Several 
 other animal matters have the same property, as 
 for instance, the cartilage and the skin. These, 
 however, have not the same texture, and pro- 
 bably not the same composition, since they can- 
 not all be completely dissolved with the same 
 ease. This glue does not exist as such in the ani- 
 mal matters, but is a product of the boiling. 
 The erroneous idea, that glue was found within 
 the living body, and was dissolved in its hu- 
 mours, has been supported by the experiment 
 of ascertaining its presence by means of infusion 
 of galls; but although many other animal matters 
 are precipitated by the tanning principle, yet the 
 precipitate with glue has this distinguishing 
 characteristic, that it clogs together into a tough 
 elastic mass, which, when dried, becomes hard and 
 brittle. Such a precipitate cannot be obtained 
 from any animal humours, except from urine, 
 after it has previously been boiled some time 
 with alkali, whereby the dissolved animal mat* 
 
ters in the urine, through the effect of the alkali 
 and boiling-, probably approximate more to the 
 nature of a glue. 
 
 The cellular texture contains in its small cel- 
 lules a particular humour, which, though it has 
 not been examined, we may upon good ground 
 consider as of the same kind with that, which is 
 met with in the cavities of the body, in blisters, 
 dropsy, &c. In some places it contains also a half- 
 fluid fat, the consistency of which may vary in dif- 
 ferent parts, but which, as to its chemical pro- 
 perties, resembles the fat oils from vegetables. 
 In the many different modes of preparation, by 
 which this fat is obtained for technical purposes, 
 it partly receives foreign mixtures, and partly un- 
 dergoes some less perceptible changes of compo- 
 sition, whereby it assumes different qualities. 
 A right knowledge of these circumstances, al- 
 though not very material to Animal Chemistry, 
 would, however, be of great consequence in 
 procuring better and more useful kinds of fat. 
 Among the productions from the distillation of 
 fat, an acid foetid water is obtained, which 
 CARTHEUSER considered to be a peculiar acid, 
 which, when combined with an oil, constituted 
 the fat. &EGNER and KNAPE also examined 
 
52 
 
 this acid, and VON CREI/L wrote an explicit 
 treatise upon it, in which he examined its proper- 
 ties, and gave it the name of sebacic acid. Se- 
 veral Chemists afterwards proposed new methods 
 of preparing- it. THENARD shewed at last, that 
 this acid consisted of the acetic and muriatic acids, 
 together with an empyrenmatic oil, of a highly 
 offensive smell, which was dissolved in it. On 
 the other hand, he found in this very oil an acid, 
 which might be extracted by boiling it in water, 
 and which, during the cooling of the water, pre- 
 cipitated itself in small light granular crystals, 
 which he considered as a peculiar acid and called 
 it sebacic acid. I have myself since found, in 
 the same acid, with the exception of a few ex- 
 ternal characters, all the properties of benzole 
 acid, and from this I consider THENARD'S seba- 
 cic acid as benzoic acid, impregnated with the 
 residuum of other products of distillation, which 
 evidently impart a smell, both to the acid and to 
 its salts, and which modify their taste. 
 
 When any part of the cellular texture is infla- 
 med, that kind of inflammation takes place which 
 is called phlegmonic. When this is suffered to sup- 
 purate, the greatest part of that which is inflamed 
 changes itself into a peculiar humour, called pus ? 
 
'which dissolves the adjacent parts, and at last, 
 -when its situation allows it, empties itself through 
 the skin. Many chemical experiments have been 
 made with this pus; the object of which, how- 
 ever, has only been to learn to distinguish it in 
 diseases of the lungs from the expectorated mu- 
 cus, that physicians might be able the better to 
 judge of the nature of the disease; but, notwith- 
 standing all these experiments, we have not at- 
 tained any satisfactory results ; however, the mu- 
 cus in the trachea aud bronchia has chemical 
 characters very distinct from those of pus, since 
 the former is very easily dissolved by acids, and 
 remains thus dissolved, and the latter requires 
 the acids to be more concentrated, and may, af- 
 ter the solution, again be* precipitated by water* 
 The reason why the methods of examination, pro- 
 posed by DARWIN, BRUGGMANS, GRASMEYER 
 and others, have had no certain results, is this, 
 that no correct distinction has been made be- 
 tween mucus and pus. They always considered 
 as mucus, the yellow matter, which is expecto- 
 rated after the crisis of the inflammation in the 
 lungs, and where no destruction of parts had oc- 
 curred. On the other hand, they considered that 
 only as pus, which is generated in an abscess or 
 in an open suppurating ulcer in the lungs* This 
 
 ;R 3 
 
54 
 
 is, however, a mistake, for both are pus (ori- 
 ginating in the coloured blood, which, during 
 inflammation, is carried into the capillary ves^- 
 sels) which exudes on the membrane of the tra- 
 chea, mixed with mucus, but whicli in the cellu- 
 lar texture has no other outlet, than that, which it 
 can procure to itself by the dissolution of the ad- 
 joining parts; hence, when chemically analysed, 
 it must be found to contain more constituent 
 parts, than the matter produced on the mucous 
 membrane. I am convinced, that by a proper 
 comparative examination, the difference might 
 be discovered, and the physician enabled, through 
 the analysis of the expectorated matter, to deter- 
 mine whether it proceeds from an open ulcera- 
 tion, or is formed only in the mucous membrane. 
 But, hitherto, we have no such examination. 
 GEORGE PEARSON has indeed lately described 
 the different varieties of the expectorated mu- 
 cous matter, and fully examined the relation of 
 the different kinds to heat, water, spirits, and ace- 
 tic acid ; he has alsp made some attempts toward 
 their analysis, which evince both attention and 
 diligent research ; but as lie could not know some 
 of the substances, which are generally found in 
 animal humours, and as he seemed to want the 
 experience, \* hich in every research is so neces* 
 
55 
 
 sary for forming a correct judgement of what we 
 see; these analytical investigations have not been 
 productive of the information which one might 
 have expected, if made hy a Chemist who had 
 also examined other animal fluids. However, 
 among the results of his experiments, there is 
 much that deserves to be noticed. In the mu- 
 cous matter, which is expectorated in long catar- 
 rhai coughs, he found, when diluted with water 
 and observed with a good miscrocope, heaps of 
 small globular bodies, which were carried to and 
 fro, as it were, with a spontaneous motion. 
 These globules were somewhat larger than the 
 globules of the colouring matter in the blood, and 
 could not be destroyed,, either by trituration or 
 boiling, nor by drying or - re-dissolving, neither 
 by coagulation with mineral acids, alcohol, 
 rether, alum, or tanning principle, nor by an 
 addition of so small a quantity of caustic alkali, 
 that the humour still kept itself turbid, and even 
 a commencing putrefaction did not break them 
 down ; but they were destroyed by concentrated 
 sulphuric acid, and by employing so much caus- 
 tic alkali, as to render the solution clear, or by 
 heating the dried matter until it began to be char- 
 red. He found these globules also in expectorated 
 pus in .a decided case of consumption; but his sup- 
 
56 
 
 position, that they consist of an organized carbon, 
 seems not a fortunate one. He also found, that 
 the thinner these expectorations were, the more 
 salts they contained, and the sooner they at- 
 tracted moisture from the air ; but this latter cir- 
 cumstance was probably only a consequence of 
 the smaller quantity of fixed matters, whereby 
 those constituent parts, which could attract hu- 
 midity, were surrounded. When, during his 
 experiments, he found the syrupy extract, which, 
 in the analysis of blood, flesh, milk, and urine, 
 I have shewn to be a composition of muriate of 
 soda, alkaline lactate, and some peculiar animal 
 matters, he considered it as an animal oxid, 
 which possessed the quality common to acids, of 
 neutralizing a certain portion of alkali so com- 
 pletely, that it was no longer discovered by the 
 re-agents. In the ashes of the burnt pus, he 
 found, besides the common constituents, also 
 silica and oxid of iron. 
 
 The loss which the humours of the body daily 
 suffer by excretions, as also that which the blood 
 must experience, from the reproduction of parts, 
 is day by day compensated by the food which is 
 eaten. Chemistry has been much occupied in 
 explaining the processes, which take place in the 
 
V 57 
 
 stomach, and in tlie bowels; and here, as every 
 where else, it has been obliged to stop short, 
 where the nervous system has begun to determine 
 the chemical state of these processes. 
 
 Through BICHAT'S excellent investigation into 
 the membranes of the body, we have acquired bet- 
 ter information relative to the vessels, in which the 
 processes of digestion are performed, and have also 
 been enabled to attain a more precise chemical 
 knowledge of the composition of the membranes 
 of vessels. The whole intestinal canal, and all 
 the reservoirs, with their excretory ducts, which 
 have any connexion with it, are coated on the 
 inside with a mucous membrane ; so called, be- 
 cause it keeps itself constantly covered with a 
 mucus, by which it is defended against any effect 
 from those bodies, with which it comes in con- 
 tact. The chemical composition of this mucous 
 membrane has been satisfactorily examined by 
 BICHAT : its principal character is insolubility 
 in boiling water we derive no glue from it like 
 that from cellular and serous membranes (M. se- 
 rosse) ; and of all parts of the body, the brain ex- 
 cepted, it is soonest destroyed by being macerated 
 in cold water, or treated with acids. The mu- 
 cus, with which the membrane is covered, is aU 
 
every where alike as to its external charac- 
 ter, but in other respects, it varies very much in 
 its chemical properties, according to the different 
 nature of the substances with which it is destined 
 to come in contact* I have, myself, found in an 
 experiment I made on the mucus, that it has cer- 
 tain varying chemical characters in the nose, in 
 the trachea, in the gall bladder, in the urinary 
 bladder, and in the bowels, without which it could 
 not answer its destined purposes. The mucus, 
 in the nature of its composition, is not a solution ; 
 but contains a solid body, which has the property 
 of swelling in water and becoming a tough half- 
 liquid mass, which, however, is not dissolved if 
 more water is added, and which may be deprived 
 of its w ater, by placing it on blotting paper, and 
 thereby rendered more dense. The humour by 
 which the mucus is penetrated is nothing else than 
 serum, which, however, has lost almost its whole 
 portion of albumen, retaining only the other consti- 
 tuent parts. The peculiar substance, which forms 
 the mass of the mucus, for instance, in the nose, 
 is soluble both in acids and in alkalies, although 
 somewhat more slowly in the latter ; but, on the 
 contrary, it is very easily dissolved, in the gall- 
 bladder, by means of alkali ; but is completely 
 precipitated by acids. By this property, the mucus 
 
59 
 
 dissolved in the bile, is precipitated by the acid in 
 the chyme, when the bile is decompounded during 
 digestion. The mucus of the gall bladder, if it 
 had the properties of that in the nose and trachea, 
 would remain in solution in the chyle, and, there- 
 by, be le>ss useful in the animal oeconomy. Se- 
 veral Authors mention an animal mucus, as a sub- 
 stance distinct from the mucus of the membranes, 
 and supposed to be found in the fluids of the ani- 
 mal body. I can only say, that in all my experi- 
 ments, I have never found any matter, to which 
 this name could be applied, or which agreed, satis- 
 factorily, with the character of those substances, 
 which HATCHETT, BOSTOCK, JORDAN, and 
 others, have designated by that name. It ap- 
 pears probable to me, that with most of them, 
 mucus has been a common name for matters, 
 which could not be distinctly specified. The cele- 
 brated FOURCROY, a little before his death, left 
 us a treatise on mucus, in the sense in which I 
 have here used the term ; but this treatise was not 
 occasioned by any direct investigation, but was a 
 mere result of scattered observations, whereby he 
 fell into an error (to him not very uncommon) of 
 drawing general and extensive conclusions from 
 very uncertain, and sometimes incorrect observa- 
 tions ; and with these ingenious and interesting 
 
60 
 
 representations, the credulous and inexperienced 
 reader has been deceived. In this treatise he 
 generalized the idea of mucus so far, that ac- 
 cording* to his statement, the epidermis, nails, silk, 
 hair, and other substances of the most different 
 chemical and physiological characters, were no- 
 thing else than hardened mucus. 
 
 The intestinal canal, besides of the mu- 
 cous membrane, is surrounded by a dense cellu- 
 lar and a muscular membrane, corresponding in 
 their chemical properties, the former with the 
 cellular texture, and the latter with the muscles. 
 On the whole of its outside, from the throat to the 
 rectum, it is enveloped by the serous membrane of 
 the abdomen. These serous membranes, which are 
 found in all the cavities of the body (to conclude 
 from the imperfect chemical experiments that 
 have been made on them) consist of the same 
 fundamental mass as the cellular texture. They 
 are called serous, because a serous fluid constant- 
 ly moistens them, and prevents their adhesion. 
 This fluid is very considerable as to its quantity ; 
 it has been chiefly collected in dropsies, and never 
 examined in its healthy state ; we have, however, 
 every reason to suppose, that its composition on 
 these occasions is not altered. Accord '.m* 1 to sonic 
 
Gl 
 
 experiments, which I have myself made, this 
 fluid consists of serum, which has lost the greater 
 part qf its albumen, of which, however, so much 
 remains, that the fluid, during boiling 1 , becomes 
 in a very small degree coagulated. During its 
 evaporation common salt is crystallized from it, 
 and the usual brown extract is deposited between 
 the crystals, containing alkali, lactate of alkali, 
 and the extractive animal matters, which com- 
 monly accompany them. 
 
 The Fluids, which some way or other contri- 
 bute to digestion, are the .sa liva, the gastric juice, 
 the bile, the fluid of the pancreas, and that of the 
 intestines, (succus intestinal is). FOURCROY and 
 VAuauELiN have left us an examination of the 
 saliva, and it has since been analysed by Bos- 
 TOCK, and lastly, I have myself endeavoured to 
 ascertain its composition. I found it to be 
 one of the most aqueous fluids of the body. 
 It contains a suspended white mucous matter, 
 which is easily separated by the solution of the 
 saliva in water, and which is soon dissolved by 
 alkali, but not by acids. I have reason to believe, 
 that, to a certain extent, at least, it originates in 
 the mucous membrane of the salivary ducts, and 
 
the inside of the mouth. The other part of the 
 saliva contains, besides the Usual salts of the se- 
 rum, a peculiar matter, remarkable in this respect, 
 that it cannot be coagulated either by boiling, or 
 by the tanning principle, or the subacetate of lead. 
 With water it resolves itself into a liquid frothy 
 solution, although it should be observed, that the 
 saliva derives its property of forming threads 
 only from the mucus, which is mixed with it. 
 The viscidity of the saliva has been considered 
 only as intended to mix small particles of air with 
 the substance, which is chewed. This, however, 
 I consider as a mistake. It may probably have 
 the mechanic purpose of preparing a slippery 
 and coherent mass from the chewed food, in or- 
 der to promote its being more easily swallowed ; 
 but it is not at all decided how far it may 
 contribute to the solution of the food. When 
 part of the mucus of the saliva remains on the 
 teeth, it thickens, gets coloured, and forms what 
 is called tartar; and I have found this to be of a 
 two-fold kind: when just settled it is clearly 
 nothing else than the darkened mucus ; but during 
 the destruction of the mucus we insensibly per- 
 ceive phosphate of lime on the enamel of the 
 tooth, which sometimes is increased to a crust of 
 
63 
 
 the thickness of \ to 1 a line. This contains, be- 
 sides the phosphate, about its weight of mucus, 
 which has been dried up in the earthy mass. 
 
 Several Natural Philosophers, both ancient and 
 modern, such as STEVENS, RE AUMUR, SPALL AN- 
 
 ZANI, SCOPOLI, BRUGNATELLI, CARMINATI, 
 
 VAUQUELIN, &c. have endeavoured to investi- 
 gate the composition of the gastric juice; but a& 
 animal fluids in general had been little examined, 
 and the greater part of these philosophers were 
 not much acquainted with Animal Chemistry, 
 all their analytical attempts were productive of 
 no satisfactory results, since they could not com- 
 pare the substances that were found in the gas- 
 tric juice with the constituent parts of other 
 fluids. VAUQUELIN always found phosphoric 
 acid in the gastric juice of herbivorous animals; 
 whilst on the other hand, that of man and car- 
 nivorous animals, had seldom any visible trace* 
 of acid or free alkali. One of the most remark- 
 able chemical properties of the gastric juice is its 
 power of dissolving the nutriments, which the 
 animal consumes, and of coagulating milk and 
 albuminous substances. The latter requires so 
 small a quantity of the coagulating matter, that 
 YOUNG found, that if the interior mucous mem. 
 
64 
 
 brane of the stomach (which after the death of 
 the animal retains in its vessels part of the gastric 
 juice, which in the moment of death was about 
 to be secreted) be first washed with water and 
 then with a weak alkaline solution, the water 
 with which it is macerated, has, even after this 
 operation, the power of coagulating- milk and 
 seium. It is not yet ascertained what substance 
 it is, that gives these distinguishing qualities 
 to the gastric juice. In the mean time, it is as- 
 serted by some, that flesh, wrapped in a fine 
 piece of linen, and afterwards placed in a situa- 
 tion, where it is penetrated by the matter of per- 
 spiration, as under the arms, between the toes, 
 &c. becomes dissolved in the same manner as by 
 the gastric juice. 
 
 The Fluid of the pancreas has never been che- 
 mically examined ; it is supposed, however, from 
 the structure of the gland, which resembles that 
 of the salivary glands, that it is analogous to the 
 saliva in its composition. The bile, on the con- 
 trary, has often been an object of chemical exa- 
 mination. BOERHAVE, BlANCHI, VERHEYEN, 
 
 HOFFMAN, DUELING OURT, HARTMAN, MAR- 
 HEER, BARCHIIUSEN,SCHROEDER, and others 
 of the old school, have occupied themselves a good 
 
es 
 
 deal with it ; but CABET gave us the first tolera-> 
 l>ly accurate analysis on the subject, and some 
 years after him VAN BOCHAUT also engaged in 
 the investigation. Those who have since la- 
 boured in this field are MACLURG, FOURCROY, 
 POWELL, and very lately THENARH. The old 
 experimenters all agreed in considering the bile 
 as a kind of soap, composed of caustic soda, and 
 a peculiar green bitter resin, which could be pre- 
 cipitated by acids, and supposing that the sapo- 
 naceous substance was mixed with the bile in a 
 certain proportion. It was also considered as con- 
 taining a portion of albumen, which could be 
 separated by alcohol ; THENARD, however, 
 shewed that the bile contained, besides this resin, 
 a peculiar bitter-sweet matter, in form of an ex- 
 tract, to which, from its taste, he gave the name 
 picromel, and which, together with the alkali, 
 contributed to hold the resin dissolved. Some 
 circumstances in THENARD'S experiments, 
 which appeared rather improbable, made me 
 also undertake an analysis of the bile, the result 
 of which was the discovery, that none of my pre- 
 decessors had properly ascertained the composi- 
 tion of it : I found that it contains no resin what- 
 ever; that it has the same proportion of alkali 
 and salts as the blood ; and that it contains a pe- 
 
 F 
 
66 
 
 cxiliar matter of a bitter and afterwards some- 
 what sweet taste, which- possesses characters iu 
 common with the fibrin, the colouring matter, and 
 the albumen of the blood, from which it is formed 
 in the liver, I found, also y that with mineral acids 
 it forms a peculiar substance, not easily soluble 
 in water. With an excess of acid it is completely 
 precipitated, and has all the characters of a re- 
 sin, viz. is soluble in alcohol, melts in heat, forms 
 a composition like a plaster with the oxid of lead, 
 8cc. A smaller quantity of acid, on the contrary, 
 produces a more soluble compound. The resin r 
 which is precipitated with sulphuric acid, may 
 be restored to its original properties by being 
 treated with carbonate of barita, and then pro- 
 duces a solution altogether like bile. This pe- 
 culiar matter agrees also with the albumen and 
 the fibrin of the blood in this respect, that it 
 cannot be precipitated by acetic acid. In dif- 
 ferent animals, as also- under different circum- 
 stances in the same species, it has a different 
 tendency to form almost insoluble combinations 
 with the acids; aad from the experiments that I 
 have had an opportunity of making, I drew the 
 conclusion, that its remaining long in the gall- 
 bladder, increases its tendency to form resin with, 
 the acids. All my predecessors have allotted a 
 
67 
 
 portion of albumen to the bile; but as the matter 
 which they have here called albumen is precipi- 
 tated from the bile by acetic acid, and cannot 
 be dissolved in an excess of acid, it must, of 
 course, be something else. In an examination 
 of the mucus from different parts of the mucous 
 membranes, I demonstrated * that this matter is 
 nothing 1 else, than a part of the mucus of the gall- 
 bladder, which has become dissolved in the bile, 
 and made it what physicians term, more in- 
 volved. The bile, however, contains it in very 
 small quantities ; for when this fluid is very thick 
 it does not afford a perceptibly greater residuum 
 after evaporation, thani when it is quite thin. 
 
 This is'all that we know of those fluids, which 
 have any thing to do with digestion ; and although 
 this process is more independent of the immediate 
 influence of the .nervous system than most others* 
 it is far from being sufficiently understood. It was 
 for a long time believed that the office of the sto- 
 mach, in digestion, was nothing elso than a me* 
 chanical effect of its membranes, in triturating the 
 food. The experiments, however, of STEVENS, 
 REAUMUR, and SPALLANZ ANI, have proved the 
 incorrectness of this supposition. They caused 
 animals to swallow tubes, and balls, of metal, per- 
 
 F 2 
 
68 
 
 fo rated with small holes, in order to admit the flu- 
 ids of the stomach ; in these they put nutritious sub- 
 stances, and they fount], that this food, after a-while, 
 was equally changed into chyme with that in the 
 other part of the stomach. A mechanical effect 
 of the coats, could not therefore be the cause of 
 digestion. "Fermentation was next resorted to but 
 when it was found, that, meat, in close balls of 
 metal, was not changed in the stomach, and that 
 small bones, which had been swallowed, were 
 dissolved and had lost their cohesion, the theory 
 of fermentation was relinquished ; and that opinion 
 was adopted, which is still considered as most 
 probable, that a peculiar fluid, the y a sir ic juice, is 
 secreted in the stomach, which possesses the pro- 
 perty of dissolving the nutritious substances that 
 enter that organ, and by this dissolution pre- 
 paring them for the further changes, which are 
 to take place in the duodenum. In consequence 
 of these ideas, SPAIAANZ ANI instituted numerous 
 experiments to ascertain the nature and property 
 of the gastric juice, the repetition of which would, 
 at present, be productive of far greater advan- 
 tages than could have been expected in his time. 
 EAGLESFIELB SMITH has endeavoured to prove, 
 by experiments on frogs, that the bile, and not 
 the gastric juice, was the means of solution, 
 
09 
 
 siure the food in the stomach of these animals 
 ivas always found unchanged if the biliary duct 
 was tied up,; but if he administered bile to them, 
 or untied the ligature, digestion was very soon 
 performed. But even should these observations 
 and conclusions be found correct, as they regard 
 the amphibia, the case is still different in the 
 mammalia; for we have many instances of per- 
 fectly prepared chyme being thrown up, in which 
 no sign of bile has been perceived, and when bile 
 at any time is met with in the human stomach, it 
 is always, according to well-established experi- 
 ence, a certain sign of disease. 
 
 EVERARB HOME has lately endeavoured to 
 prove, that the stomach, during the time of di- 
 gestion, is kept divided*into two parts by its mus- 
 cular fibres. He supposed that the portion nearer 
 to the throat is destined to contain liquid nutri- 
 ments, and that in the more remote the solid nutri-, 
 fious substances are to be dissolved. The object 
 of this division of the stomach, during the pro- 
 cess of digestion, which certainly seems not very 
 probable, he supposes to be, to convey the greater 
 part of those fluids through an unknown channel 
 from the stomach into the spleen, that they may 
 mix with the blood more speedily, than by the 
 
70 
 
 course of the absorbent vessels from the intestiim 
 canal. This passage, which could not be alto- 
 gether unexpected by those who were acquainted 
 with the minute investigations, which were for- 
 merly instituted to discover a direct way from 
 the stomach to the kidneys, HOME has endea- 
 voured to support, by .experiments, which, in 
 case they have been correctly observed and 
 confirmed by other experiments, do certainly 
 prove the point most completely. He found, 
 for instance, that when a person takes a dilute 
 infusion of rhubarb, the colouring matter of 
 the rhubarb shows itself about twenty minutes 
 after, in the urine, but soon disappears again, 
 unxl does not return till after several hours, when, 
 the remainder of the infusion of rhubarb has 
 passed the thoracic duct. When an animal is 
 made to take infusion of rhubarb, and is killed 
 shortly after, the infusion is discoverable in the 
 blood of the spleen, but not, for instance, in 
 that of the liver, &c. Tie found, that the spleen 
 contained a number of small cellules filled with 
 % colourless fluid during the period of diges- 
 tion; but which, at other times, were collapsed 
 and almost imperceptible. The same observa- 
 tions, relative to the structure of the spleen, 
 also been made by other respectable 
 
71 
 
 tomists before HOME, In this manner the 
 chyme always acquires a determined consistence, 
 since the superfluous fluids, which have been 
 swallowed, are emptied without being- mixed 
 with it; while the chyme is conducted through the 
 pylorus into the duodenum, where it comes in 
 contact with the bile. The change, which the 
 bile here undergoes, is unknown, both as to its 
 nature and its purpose. That it is really decom- 
 posed, we may learn from this circumstance, that 
 it is no longer met with in the contents of the in- 
 
 O 
 
 testines as bije ; but instead of it, they contain the 
 peculiar matter of the bile, changed into a kind 
 of yellow or greenish adipocerous fat, which gives 
 to these contents their darker colour. It was 
 thought that no chyle could be formed w ithout 
 the assistance of the bile, and though it cannot be 
 denied, that the bile may be indispensable for 
 the formation of perfect chyle, yet we have in^ 
 stances of persons, in whom, during the course 
 of a chronic jaundice, the flow of the bile has 
 been obstructed for two or three weeks together, 
 and yet they have not died for Want of nutriment. 
 After the bile and the pancreatic juice have mixed 
 themselves with the chyme, we find it distinctly 
 divided into a kind of white eyiulsigu, which. 
 
72 
 
 from its colour, is called lacteal fluid or chyle, 
 and another light yellow insoluble part, which i* 
 destined to form an excretion. This insoluble 
 part consists of such parts of the food, as can- 
 not be dissolved by the gastric juice, and of thf 
 bilious matter, which is precipitated in the form 
 of a coloured adipocere, and probably in this state 
 is united to certain parts of the chyme, which, by 
 their affinity, have determined its precipitation. 
 Both are now blended together. The absorbents, 
 which arise every where in the vilious surface of 
 the mucous membrane, absorb the ^dissolved part 
 and leave the midissol ved j but as the mass, by 
 means of this absorption, would at last become 
 very dry, before the whole of the chyle had 
 been taken up, a thin liquid humour is secreted 
 on the inside of the intestines, which unites it- 
 self with it, dissolves the chyle, and is afterwards 
 absorbed by the succeeding portions of the intes- 
 tines, so that when their contents arrive at the 
 sphincter, there is often none of the chyle left 
 in them. The nature of this mass, after excre- 
 tion, has been very little examined by former 
 Chemists; and the experiments which VAU- 
 QTJELIN and SAGE in later times have left us, 
 cannot be considered as complete, 
 
73 
 
 EIXHOF and THA.ER instituted a very minute 
 * xanunation of the excrements of cattle, and I 
 have since examined those of man in a more phy- 
 siological point of view than my predecessors. 
 These contain about j of their weight of fluid, in 
 which is found, besides the small portion of yet 
 undecompoundecl bile, a solution of the usual salts 
 of the serum, a certain quantity of phosphate of 
 magnesia, and a peculiar animal matter in form of 
 an extract. The solid mass consists of what is un- 
 dissolved in the stomach, or precipitated in the 
 duodenum, and of the mucus of the intestines, 
 which is thoroughly diffused through the whole 
 
 mass. 
 
 *le 
 
 VAUQUELIN instituted a comparative experi- 
 ment on the quantity of earths a hen consumed in 
 the oats on which it was fed, and the quantity 
 produced in the eggs and excrements, whereby it 
 appeared, that the quantity of phosphate of lime in 
 the latter was twice as much as in the former, 
 besides a quantity of carbonate of lime, found in 
 the oats on which it was fed, and that the quan- 
 tity of silica was somewhat, though not consider- 
 ably, diminished in the excretions of the hen. 
 These experiments, which, by the bye, have been 
 
74 
 
 made very intricate by incorrect decimal cyphers 
 and erroneous calculations, seem to prove, what 
 experiments with vegetables further confirm, that 
 these earths must be capable of being composed 
 and decomposed, as occasion requires, by the 
 processes of organic chemistry. 
 
 The Chyle, such as it occurs in the smaller in- 
 testines and in the first branches of the absorbent 
 vessels, is not distinctly known. From its colour 
 and its property of coagulating, whilst boiling, it 
 was compared to milk, and it was long supposed 
 that its principal constituent parts consisted of 
 sii^s ir of milk. This error is, however, now cor- 
 Xyjted. As soon as the chyle has come into the 
 thoracic duct, its milky colour gets more and 
 more faint in proportion as it is diluted with 
 lymph from other absorbing vessels. In general 
 it is a mixture of yellow and grey, is coagulated 
 in the air, and the coagulum assumes, by degrees, 
 a red colour. We have, consequently, reason to 
 consider the suspended white and grey matter in 
 the chyle as a colouring matter not yet com- 
 pleted, and which wants the contact of the air, in 
 order to be perfected. The experiment on the 
 chyle, by HALLE, EMMEIVT, and REUSS, all agree 
 
75 
 
 in tliis, that chyle, except in the colour, resembles 
 blcod, but is a much more dilute fluid. After 
 FOURCHOY had stated that the colouring matter 
 of the blood was a combination of red subphosphate 
 of iron with albumen, it followed, that the white 
 colouring" matter in the chyle must be albumen 
 united with a neutral phosphate of protoxid of iron, 
 which at its entrance into the blood acquired an 
 excess of base by the alkali of the blood, and which 
 was changed in the lungs from protoxid to pe- 
 roxid ; but as no such ferruginous salt can be dis- 
 covered in the colouring matter of the blood, all 
 this seducing supposition falls to the ground. 
 
 A summary idea of the formation of the chyle 
 by digestion, may thus be expressed in a few 
 words: the alimentary matters are accurately 
 triturated in the mouth, received into the stomach, 
 and there converted by the gastric juice into'a 
 uniform fluid, which is precipitated in the duo- 
 denum by the bile. The solution is filtered in 
 the intestines by means of the absorbents, and 
 the precipitated matter is washed by the intes- 
 tinal fluid, which is again absorbed, in the same 
 manner as precipitates are edulcorated in our 
 common filtering apparatuses, after which the 
 washed mass is evacuated. 
 
76 
 
 The composition of the mass of the liver and 
 the spleen has not been examined. It has only 
 been observed, that the liver, when putri tying, 
 so far partakes of the property of the bile, as to 
 be easily changed, under certain circumstances, 
 into a substance resembling adipocere. 
 
 The texture and constituent parts of the bones 
 have only of late been accurately ascertained, 
 although it was discovered, very early, that the} T 
 contained an animal combustible part, and an 
 imorganic earthy part, which, as it did not resem- 
 ble any other earth then known, was called bone- 
 earth, or animal earth. PAPIN, HERISSANT, 
 LESSONE, and above all, HAIXER, have proved, 
 that the combustible part was cartilage, which 
 might be dissolved into a glue by boiling. The 
 nature and composition of bone-earth was disco- 
 vered by a gentleman, whom we have the happi- 
 ness of seeing this day amongst us, I mean our 
 colleague G. GAHN. This, as well as several 
 other of his discoveries, have been ascribed to 
 SCHEEXJE and BERGMAN, because these gentle- 
 men, to whom we were accustomed to ascribe so 
 much, were the first to communicate them to the 
 
 * 
 
 public, though with an unintentional omission of 
 Ins name. It was enough for this modest natural 
 
77 
 
 philosopher, that truth was made known. He 
 did not claim the honour of the discovery, since it 
 was indifferent to him, if his former Instructor or 
 his Friend were supposed to have found out what 
 he, himself, had discovered ; but posterity will 
 not forget to make amends for the neglect or 
 omission of contemporaries. SCHEELE, in his 
 treatise on the fluor spar and its acid, stated that 
 bone-earth, " as was proved by a late discovery," 
 consisted of phosphoric - acid and lime, and this 
 expression gave rise to the mistake, for the disco- 
 very was made by GAHX. 
 
 FOTJRCROY, a long time afterwards, proved, 
 that the bones of herbivorous animals contained 
 phosphate of magnesia, which he, in vain, sought 
 after in those of man ; and at last MORICHINI, 
 .an Italian, discovered, that ivory, as well as the 
 enamel .of the teeth, contained fluate of lime. 
 Besides the constituent parts which were al- 
 ready known, I have, by minute analysis, detect- 
 ed in human bone, fluate of lime and phosphate of 
 magnesia ; and I have proved, that the sulphate of 
 lime, 'which after combustion is found in them, 
 does not belong to them in their living state. 
 The cartilage of the bones I found to be about $ 
 part of their mass. It was somewhat less in the 
 
ts 
 
 teeth, and entirely wanting in the enamel of the 
 teeth. FOURCROY and VATJ&TJELIN had found 
 27 p. c. combustible matter iii the enamel. PE- 
 1YS only 16 p. c* but I could not find 2 p. c. of 
 it. MERAT-GTJILLOT has instituted a compara- 
 tive investigation on the bones of several ani- 
 mals ; but it has produced very incorrect results. 
 While I found* for instance, in the human bones 
 and those of the bullock, the same constituent 
 parts, and nearly the same proportions, he found 
 93 p. c. phosphate of lime in the latter ^ and 67 in 
 the former. The cartilage, which is the ani- 
 mal constituent part of the bones, is so closely 
 united with the bone-earth, that they constitute a 
 common whole, of a texture, which withstands 
 considerable impressions, and of a chemical com- 
 position, which, when the bones have not been 
 moistened, has preserved itself unaltered for se- 
 veral centuries. In later times w r e have known 
 how to profit by PAPIN'S excellent discovery, of 
 extracting from bones a good and salutary nutri- 
 ment, which in his days was disregarded. PAPIN 
 had shown to Charles II. of England, that it was 
 possible to extract a jelly from the bones, and had 
 engaged within 24 hours with eleven pounds of 
 charcoal to prepare 150 pounds of a jelly, which 
 he recommended to be used in workhouses and m 
 
79 
 
 hospitals. The King was ready to give this 
 project the attention it deserved, when, as he was 
 one day going- to dinner, he found petitions fas- 
 tened to the necks of his dogs, the import of which 
 was, that he should not deprive them of a food, 
 which they had long considered as their proper- 
 y. The jest was smiled at, and PAPIN'S disco- 
 very was lost for the age. L. PROTJST recalled 
 the public attention to it, and proposed to the 
 Spanish government to use the bones for the sol- 
 diers, and in public institutions for the poor, and 
 his proposal was adopted. The French govern- 
 ment, observing the progress of their neighbours, 
 ordered this matter to be investigated in France, 
 where it was soon adopted, and afterwards spread 
 itself throughout Europe. Several learned men 
 have occupied themselves with experiments for 
 extracting the cartilage of bones completely, and 
 it has almost generally been found impracticable, 
 except by using PAPIN'S boiler, on which such 
 improvements have been made of late, that it 
 may now be used without any danger. Some 
 have gone so far in their zeal for the bone soup, 
 that they have considered bones as more nutri- 
 tious,and consequently of more value, than an 
 equal weight of meat. This, however, is not cor- 
 
80 
 
 rect, for the reasons, which I have slated in the? 
 analysis of muscular fibre. 
 
 On the composition of the bones, according tu 
 the different age of the individual, \ve have no 
 satisfactory experiments ; neither do we know 
 the general differences of the bones of different 
 classes of animals. HATCHETT has examined 
 the integuments or coverings of the testacea, which 
 we justly consider as the bones of those animals, 
 and he found them to be composed of a peculiar 
 animal matter, the nature and chemical proper- 
 ties of which he did not minutely determine, and 
 of carbonate and phosphate of lime. While the 
 bones of the mammalia consist of phosphate of 
 lime with but little carbonate, these shells, on the 
 contrary, consist of carbonate of lime with a few 
 p. c. of the phosphate. 
 
 Marrow, or the fat, which is contained in the 
 long bones, appears, by my experiments, to be 
 similar to fat in other parts of the body and the 
 different properties it acquires by being boiled 
 whilst included in the bone, belong entirely to 
 the fluids, contained in the vessels of the proper 
 membrane of the marrow, and which it loses 
 altogether, when the fat is melted from its cells. 
 
81 
 
 The composition of cartilage is exactly the 
 same as that of the cartilage contained in bones. 
 It is dissolved by being boiled in water, and is 
 changed to a glue, its veins and nerves remaining* 
 undissolved. 
 
 The Stnovia, contained in the joints between 
 the bones, has been examined by MARGUERON, 
 a Frenchman. It seems to be almost completely 
 serum, which has retained its portion of fibrin, 
 for it coagulates in atmospheric air : this co- 
 ngulum, however, i not coloured, and the rest 
 is entirely similar to the fluid in coagulated 
 blood. When MARGEURON stated the proper- 
 ties of fibrin in this humour to be 12 p, c. he 
 weighed it, most probably, in that moist state 
 in which it is found on coagulation. This fibrin 
 has not altogether the same properties as the fi- 
 brin of the blood, but from his analysis no very 
 precise knowledge of the difference can be de- 
 rived. FOURCROY seemed to think that it was 
 uric acid, for which opinion there appears to be 
 no other reason, than that gouty concretions, 
 which consist of urate of soda, are sometimes 
 formed near the joints, and obstruct their motion. 
 
 The Muscles, (or what is ' generally termed 
 flesh) have been less examined than oth ?r animal 
 
82 
 
 matters. GEOFFROY endeavoured to ascertain 
 how much could be extracted from them by wa- 
 ter, and the different quantity of nutritious sub- 
 stances, which might he obtained from the flesh 
 of different animals. THOUVENEL next gave 
 us an analysis of flesh, which he considered as com- 
 posed of the muscular fibres, properly so called, 
 and a peculiar extract, soluble in alcohol and 
 water. I have since found, that flesh contains 
 near I of its weight of fluid ; that this fluid con- 
 tains a, free acid, and that the extract, which 
 THOUVENEL, described, is the same acid sy- 
 rupy mass, which is met with in milk and urine, 
 and which consists of lactic acid, lactate of alkali, 
 salt, and the animal matter, which is united with 
 these salts in the form of an extract. I have en- 
 deavoured to prove that this extract is not a con- 
 stituent part of the flesh, but that it has belonged 
 to the absorbents, and that it consists principally 
 of the decayed particles, which have been either 
 absorbed by them, or were ready to be absorbed 
 when life was extinguished. The fluids of the 
 ilesh abound much more in this syrupy extract, 
 and contain more phosphate of soda, than the 
 blood j and from this, I have concluded, that those 
 matters, which are formed by the decay of the 
 parts, are absorbed and introduced into the blood, 
 in order to be. discharged with the urine, in which 
 
they are again discoverable in a considerable 
 quantity. The solid living- muscular fibre is, as 
 anatomy will shew, interwoven with the cellular 
 texture, and furnished, even in its innermost 
 parts with veins and nerves. This fibre has the 
 same qualities with the fibrin of the blood ; it is 
 soluble in acetic acid, except the greater part of 
 the cellular texture, together with the vessels and 
 nerves whereby it is supported. The fibrin of 
 the flesh undergoes the same change by boiling 
 as that of the blood ; it thereby becomes insoluble 
 in acetic acid, and leaves to the water, with 
 which it has been boiled, a constituent part, 
 which has a strong and pleasant taste of flesh 
 and cannot be gelatinised. When this is disr 
 holved, together with the cellular texture, and 
 mixes itself with the uncoagulated part of the liu^- 
 mours of the flesh, it forms what we call broth, 
 the strength and taste of which depends not only 
 on the dissolved and glutinised ceilula^ UiXture, 
 but also, on the fibrin, the taste of wliidh it retains. 
 The difference between the tasteless bone-soup 
 and the broth, has formerly been ascribed to the 
 extractive substance ; but this cannot be correct, 
 since we know that flesh, the humours of which 
 have been extracted, gives a very palatable and 
 nourishing, though at the same time, colourless 
 soup, & 2 
 
84 
 
 Various experiments have been made to dis- 
 cover the intimate nature of the motion of the musr- 
 cles. CARLISLE has endeavoured to prove, by se- 
 veral very ingenious methods, that a muscle, while 
 it contracts, increases in weight and volume, and 
 is consequently penetrated by an increased quan- 
 tity of fluids. The most probable account of the in- 
 terior mechanism by which the motion of the mus- 
 cle is produced, seems to be, that the fibres must 
 
 twist themselves round more distended vessels 
 
 > 
 
 whereby the muscle in a particular place becomes 
 shorter and thicker. It is necessary that nature, 
 by the mechanism of this internal action, should 
 endeavour to regain what it loses by that of the 
 external, in w ? hich every thing is conducted ac- 
 cording to principles, altogether contrary to those, 
 by which we are generally governed in mechanics. 
 The muscle, by means of a small contraction, 
 makes an extended motion, and consequently 
 exercisfe its power near the fulcrum of the bone, 
 whilst the counterpoise is on the other remoter 
 end of the bot\e. .Nature seems here to be lavish 
 in the power it bestows, since every muscle must 
 make a far greater effort, than would be necessary 
 under opposite circumstances ; this expenditure 
 of power must, however, certainly be balanced 
 fry the methods employed to shorten the smallest 
 
8o 
 
 fibres in the acting muscle. I have often de- 
 termined to examine, with a compound micro- 
 scope, the contraction of a naked muscle in a 
 living* animal, being convinced that by that 
 means something 1 might be obtained toward a 
 nearer explanation of this highly interesting prb- 
 cess of animal mechanics; but I have always 
 been deterred by an insurmountable aversion 
 to see a wounded animal suffer under the hand 
 of an experimenter, much as I at the same time 
 value the important physiological truths, which 
 have been discovered in this way. 
 
 Sinews, (tendons and aponeuroses) are parts of 
 the muscles, by which they are fixed to remote 
 bones, or to circumscribed points of attachment. 
 They have a mechanically strong composition, and 
 Jtre formed from the same fundamental mass as 
 cellular texture smd cartilage, from which they 
 seem to differ only in their structure. They are 
 softened by degrees by boiling, and dissolved into 
 a glue, so that at last, the veins only remain 
 undissolved> 
 
 Of the Membranes of the Eye, and the humours 
 which are contained in them, Chemistry has had 
 to record little else, than the observations, which 
 have been accidentally made by Anatomists. 
 
 G 3 
 
GHENEVIX, not long ago, gave us an analysis of 
 the humours of the eye, and I have since examined 
 their composition, together with that of the mem- 
 branes. 
 
 The Sclerotic^, which surrounds the eye on the 
 outside, has the same component parts as the 
 tendons : it dissolves by continued boiling ra wa- 
 ter, and the solution, whilst cooling, hardens into 
 a jelly. The Choroidea, spread over its internal 
 surface, is a similar compound, and in like man- 
 ner dissolves in boiling, with the exception only 
 of its numerous veins,, and the black colouring 
 matter, or pigmentum nigriun,. with which it i& 
 covered. The black substance is indissoluble ra 
 hot or cold water, and also in acids. It is solu- 
 ble, however, in caustic alkali, and the precipi- 
 tate by an acid is somewhat paler. It burns like 
 a vegetable substance, and leaves the same ferru- 
 gineous ashes as the colouring matter of the 
 blood, from which it has, in all probability, been, 
 formed and secreted, the veins of the choroidea 
 transmitting only the colourless parts into the sub- 
 stance of the eye. The Cornea, also, consists of 
 a mass, which by boiling, is converted into a glue. 
 The Iris, on the contrary, has all the chemical 
 characters of a muscle, and its constituent parts 
 
are the same as those of muscular fibre. As its 
 operation also resembles that of these organs, it 
 seems more than probable, that it ought to be con- 
 sidered as one of the muscles of the body, and in 
 man, as one of those, which.are not under the con* 
 trol of the will; although, on the other hand> its 
 motion in several birds (for instance, the genera 
 strix and psitacus,) seems to depend on the will. 
 
 The humours which fill the globe of the eye 
 are three, viz* the aqueous humour, the crystaline 
 lens, and the vitreous humour. The first and 
 the last of these humours are very thin, and agree 
 in their composition altogether with the fluid of 
 the serous membranes ; but they are distinguish- 
 ed from them in this, that they are completely 
 void of colour, and the aqueous humour seems to 
 contain a smaller quantity of albumen. The 
 crystaline lens, on the contrary, is very remark- 
 able, both as to its texture and its composition* 
 Its density is least of all at the surface, but con* 
 tinues to increase towards the interior ; and CHE- 
 NEVIX found, by removing the coats or layers 
 successively, that its specific gravity increased, in 
 proportion as he approached the centre, When 
 the process had been performed on a lens weigh- 
 ing 30 grains, with a specific gravity of 1,076, 
 
 G 4 
 
until only 6 grains remained, the specific grav/ty 
 of this internal nucleus proved 1,194. CHE- 
 NEVIX, and before him FOURCUOY, state, that 
 the lens consists of albumen and glue ; and yet 
 it contains neither the one rior the other : it 
 is almost completely soluble in water, and the 
 solutioli is coagulated on boiling; but the. coagu- 
 lated mass does not resemble albumen, it is gritty 
 and opaque, exactly like the colouring matter of 
 the blood, which it resembles also in being easily- 
 dissolved in acetic acid, after the coagulation 
 The coagulum is as white as snow,, and leave* 
 after combustion a small quantity of ferrugineous- 
 ashes. As far as we can discover, it differs only 
 from the colouring matter of the blood, by its 
 want of colour. It is not improbable, that the co- 
 louring matter is divided into the colouring part 
 strictly so called, which is deposited in the cho- 
 roiclea, and the un coloured albuminous funda- 
 mental substance, which passes on and forms the 
 crystalline lens ; although they do not receive 
 their blood from the same, but separate branches 
 of one and the same artery that is, the ophthal- 
 mic. Some attempts which have been made ta 
 change a dissolved lens into colouring matter, by 
 adding to it phosphate of iron, in various modi- 
 fications, have not been more successful thai*. 
 
 
89 
 
 similar experiments with serum. The crystalline 
 lens forms the limit between the humours and 
 solid animal matter. It contains little more than 
 half its weight of water, and differs from other 
 secreted fluids in this, that it is less aqueous than 
 blood. It produces, when analysed, a portion of 
 acidulous extract, in which it resembles animal 
 matter, divested of its alkali. KEIL, had found, 
 that when the crystalline lens is treated with 
 dilute nitric acid, it is converted into a yellow 
 fibrous mass, like raw silk, its fibres diverging- from 
 the centre towards the surface, in a certain regu- 
 lar order. From this he concluded, that the lens 
 was a muscle, whose fibres were only rendered 
 visible by this treatment ; but, although the inte- 
 rior construction of the lens is as yet too little 
 known, to- enable us to explain the mechanism of 
 the phenomenon* still it is clear, from the solubi- 
 lity of the mass in water, and from its manner of 
 coagulation, that the lens cannot possess the pro- 
 perties of a muscle. 
 
 The Tears have been examined by FOUR- 
 CROY and VAUQUELIN They resemble very 
 much the humours from serous membranes, and 
 the humours of the eye, but with this difference. 
 
90 
 
 that, instead of albumen, they contain a peculiar 
 matter in solution, which is not coagulated by the 
 heat of boiling water or by acids, but which, dur- 
 ing a slow evaporation in atmospheric air, is 
 changed into an insoluble mucus, like the mucus 
 of the nose, already mentioned. If this peculiar 
 matter, which in my Treatise on Animal Che- 
 mistry, I have called tdrd?nne, or a peculiar mat- 
 ter of the tears, possesses the characters, which 
 the French Chemists have ascribed to it, it docs 
 indeed deserve to be fully investigated. Should 
 their statement be confirmed, the mucus of the 
 nostrils must then, like the tears, be secreted in a 
 thin liquid state, and be converted during respi- 
 ration, by the agency of the air, into mucus. 
 This would presuppose an essential difference be- 
 tween the formation of the mucus in the nose, 
 and in those places, where it is not in contact 
 with the air, and must be directly secreted as a 
 complete mucus. 
 
 The Cerumen of the .Ear has been examined by 
 VAUQtJELiiy. When observed after having 
 been long detained in the meatus extrnus of the 
 ear, it is dried up, and consists of a peculiar fat 
 body resembling oil, which assumes the form of 
 an emulsion by its combination with albuminous 
 
matter. In the first moment of secretion it forms 
 a thin yellowish milk, which thickens by degrees 
 as it loses its water. 
 
 Respecting the Skin, and the parts connected 
 with it, our chemical information is hitherto very 
 imperfect. What we know is chiefly obtained 
 from accidental observations in tanning 1 and glue 
 
 O c5 
 
 making. The skin (or hide) changes by long boil- 
 ing into a glue, which is better and more tena- 
 cious in proportion as the skin is more difficult of 
 solution. Tanning consists in combining the 
 unchanged mass of the skin with tanning matter 
 from vegetables. This tanning matter, extract- 
 ed from various vegetables, often differs as much 
 in its nature, as the hides of different animals ; 
 and from this circumstance, the results will vary 
 according to the vegetable, Hvhich has been used 
 in the tanning process. Skin requires a certain 
 preparation previous to tanning. The object of 
 which is, by means of a liquid, to penetrate and 
 widen all the cells of the hide, in order to open 
 a sufficient space for the reception of. tanning 
 matter. Weak alkalies have a better effect here 
 than water, and acids succeed even better than 
 alkalis. Vegetable acids are prefered to mineral. 
 The quantity of acid in the water, with which 
 
92 
 
 the hide is soaked, may be very small, and yet 
 produce a considerable effect. The principle 
 thing to be observed in tanning- is, that it be done 
 slowly, week infusions only being used in the be* 
 ginning of the process. The more slowly the 
 process is conducted, the better the leather be- 
 comes ; whilst, by a hasty process, the outer part 
 of the hide is supersaturated with tanning matter, 
 and the avenues to the interior parts are closed ; 
 hence a hard, brittle, and thin leather is pro- 
 duced* 
 
 The Rete Mucosum, or net of Malpighi, which 
 constitutes the secretory organ of the skin, and 
 in which its nerves and absorbents are dispersed, 
 has not been examined. We only know, that 
 its black colour, observable in the skin of negroes, 
 may be bleached for some days by the applica- 
 tion of oxy-muriatic acid. The texture of the 
 Epidermis is very peculiar : It is not dissolved 
 even by long boiling in water, but it is dissolved 
 both by caustic alkalies and acids, and, in most of 
 its chemical properties, resembles the hair and 
 the nails. The greasy substance, with which it 
 is covered, has not been examined on the human 
 skin ; but VAUQUELIN has made an experiment 
 on that, which adheres to the wool in sheep, ad 
 
93 
 
 has found it to contain, besides carbonate of al- 
 kali, albumen and the acetates of lime and pot- 
 ash, a peculiar saponaceous combination of pot- 
 ash, lime and a resinous oily substance. He ascribes 
 the fat of the wool and the hide to a part of the 
 oil, which has been separated on the combination 
 of the alkali with carbonic acid from the air. 
 There appears, however, to be a contradiction in 
 supposing-, that the greasy humour should at once 
 contain carbonated alkali and lime in solution. 
 VAUQUETxiN and BUNIVA found a greasy mat- 
 ter, resembling' cheese, on the skin of the foetus, 
 whereby its epidermis in the womb was defended 
 from any effect of the liquor anmil. 
 
 The Skin is an organ of secretion, which is dis- 
 tinguished from all others by presenting an ex- 
 tended surface, from which the greatest part of 
 the secreted matter must be discharged by means 
 of evaporation. In former times much pains 
 were taken to examine the quantity of transpira- 
 tion. SANCTORIUS continued his experiments 
 for thirty years ; and after him many others have 
 laboured in the same field, as DODART, KEIL, 
 ROBERTSON, RYE, LINING, and at last also 
 LAVOISIER and SEGUIN in France, and CRUIK-, 
 in England, But all their experiments 
 
91 
 
 went only to prove, how much moisture was per- 
 spired, without affording- any information as to 
 the quality and nature of the perspired matter. 
 According 1 to the mean of these experiments 4-j 
 pounds per day, were perspired from the skin. 
 The secretion was most abundant during the time 
 of digestion, and least of all, immediately after 
 meals. CRUIKSHANK having confined his hand 
 in a glass, collected the water which transpired, 
 and found it to be very pure. In the air, a por- 
 tion of carbonic acid was found, which in all pro- 
 bability had been formed by the operation of the 
 air on the transpired matter, as the volume of the 
 air had not increased. As he obtained more water 
 in a low temperature than in a high one, he con- 
 cluded, that the transpiration of the skin was 
 greater in a low temperature; but it seems that 
 he did not recollect, that the more water was 
 condensed on the glass by cold, the greater be^ 
 came the power of the inclosed air to receive 
 evaporating water, when it was warmed again 
 by the hand. THENARD collected the matter 
 of transpiration in flannel shirts, and found, that, 
 after extracting it with water, and then evapor-r 
 ating that water, it produced an acid, saline, 
 syrupy extract, the free acid of which he consi- 
 dered as acetic, in consequence of an experiment 
 
95 
 
 in the course of his examination of the lactic acid, 
 which had determined him to declare this acid 
 to be acetic. 
 
 The matter of transpiration is always acid, 
 and reddens litmus paper very distinctly. I col- 
 lected some drops of sweat on a watch glass, and 
 suffered them to dry, when they presented crys- 
 tals of muriate of soda, and also visible marks of 
 the usual acid extract of the secretions ; on the 
 addition of water, they left an insoluble residuum, 
 which, when strongly heated, smelt like burnt 
 albumen. In the mean time, much remains to 
 be known on the subject of transpiration, before 
 we can discover the various matters secreted by it 
 from the body, and the different modifications to 
 which it is subject, according to different cir- 
 cumstances. 
 
 The Nails, which are a continuation of the 
 skin, are of exactly the same composition as the 
 epidermis; but have a firmer texture. And of this 
 nature are also hoofs, talons, claws, and such 
 other parts, as in the brute creation answer the 
 purpose of nails. 
 
 The Hair is of a peculiar composition. 
 , and Ac HARD have made several experi- 
 
95 
 
 ments upon it, and VAUQUELIN has given us*, a 
 complete examination of the subject. The re- 
 sult of his analysis was, that the mass of the hair 
 is insoluble both in cold and boiling water, but 
 that it may be dissolved in PAPIN'S digester: 
 the fluid thus produced does not form itself into 
 a jelly, but becomes viscid as it' dries. In this 
 solution, and also when the hair is dissolved in a 
 very dilated caustic lye, or in nitric acid, an 
 oil is produced, which has the colour of the hair. 
 From this very oil, YAUQTJEJLIN deduces the 
 different colours of the hair, and he found in the 
 ashes of black hair, besides the usual sails of lime, 
 oxycl of iron and of manganese and silica. Red 
 hair, which contains more sulphur than the black, 
 left less iron and manganese in the ashes; and 
 \vhite hair left still less, but its ashes were found 
 to contain a distinguishable quantity of magnesia. 
 
 Urine has undergone more chemical examination 
 than any other animal matter, VAN HELMONT 
 gave us the first experiment upon it in his trea- 
 tise on the stone. BRANDT and KUNKEL, twen- 
 ty-five years afterwards, discovered phosphorus, 
 which they prepared from the constituents of 
 urine. BOYLE, in consequence of their dis- 
 covery, tried to analyse this fluid, and actually 
 
97 
 
 produced phosphorus from it, which he afterwards' 
 caused to be prepared by HANKWITZ, an Apo- 
 thecary in London, for the natural Philosophers 
 of Europe! About the same time, another 
 analysis was instituted by LORENZO BEL- 
 LINI, an Italian, who found urine to be com- 
 posed of water, earth, and salts. It was after- 
 wards examined by BOERHAAVE, whose analy- 
 sis, considering- the time in which it was made, 
 was an excellent performance. Several others, 
 such as MARCGRAFF, POTT, HA.UPT, SCIILOS- 
 
 SER, SCHOCKWITZ, BERGMAN, KLAPROTH, 
 
 Sic. occupied themselves with examining 1 the 
 phosphates, which are contained in urine, and en- 
 deavoured to improve the methods of preparing 1 
 phosphorus from it. The younger ROUELLE'S 
 analysis of urine is even at this day of very consi- 
 derable merit. He discovered its peculiar and 
 characteristic constituent, which he called sapo- 
 naceous extract; he explained what salts are 
 contained in it, and compared the urine of men 
 with that of herbivorous animals, showing that 
 the latter did not contain phosphates, but carbo- 
 nate of lime, and benzoic acid. Some years 
 afterwards SCHEELE discovered, that the urine 
 of man contained phosphate of lime, dissolved in 
 an excess of acid, uric acid, which till his time 
 
 H 
 
08 
 
 was unknown, and benzole acid, which, however, 
 for the most part occurred only in the urine of 
 children. CRUIKSIIANK, who was employed by 
 HOLLO to examine diabetic urine, instituted af- 
 terwards an exact analysis of human urine, as 
 well in its healthy state, as in various diseases, 
 and hence very important results were obtained. 
 He described the urea showed its property of 
 being precipitated by nitric acid, and stated cer- 
 tain methods to determine with precision the re- 
 lative quantities of the different constituent parts. 
 His experiments on the urine of sick persons have 
 given Physicians very good diagnostic signs, of 
 which none, who practice medicine, ought to be 
 ignorant. Thus he found, for instance, that urine, 
 during the state we call fever, acquires the pro- 
 perty of being precipitated by corrosive subli- 
 mate. In a higher fever it is precipitated by 
 alum, and in still higher degTees, by nitric acid. 
 In common dropsy he found albumen in the 
 urine in considerable quantity, as also, though in 
 less quantity, in indigestion ; but, on the other 
 hand, its quantity was not increased in encysted 
 dropsies, &c. CRUIKSHANK'S work was pub- 
 lished in 1797, as a part of HOLLO'S treatise on 
 Diabetes mellitus. Three years afterwards, 
 FOURCROY and VAVQUELIN published a still 
 
99 
 
 more extensive and very accurate analysis of the 
 urine, and FOURCROY asserts on this occasion, 
 (in his Systeme des Connoissances Chymiques) 
 that he and VAUCIUELIN had known the circum- 
 stances, which constituted the most remarkable 
 part of CRUIKSHANK'S analysis, several years 
 before that Chemist. FOURCROY and VAUQUE- 
 LIN examined the phenomena of the putrefaction 
 of urine, and the decompositions and new combi- 
 nations which take place in the process, and their 
 work was the most complete analysis in Animal 
 Chemistry, at that time known. PROUST has 
 since made further experiments on urine, and 
 has found in it carbonic acid, carbonate of lime, 
 and a peculiar resin, like that of the bile, which, 
 however, seem all to have been formed in 
 the operation. THENARD has since endea- 
 voured to show, that the free acid in the urine is 
 not phosphoric acid, but acetic. Last of all, I 
 have taken up the investigation of this subject, 
 and have obtained results which have escaped the 
 attention of my predecessors. I found that the 
 free acid of the urine was not acetic, nor phos- 
 phoric acid ; but that it belonged to two acids 
 peculiar to the body, viz. the lactic and the uric 
 acid j and I have proved the presence of the for- 
 mer in urine, by several experiments, which I 
 
 H 2 
 
100 
 
 think tolerably decisive. In the bone-ear tlr, 
 which is held in solution by the free acid of urine, 
 I found, as in the bones, fluate of lime, and by a 
 comparison with the composition of the blood, it 
 appeared, that the kidneys, in the formation of 
 urine, oxidate a portion of the more remote con- 
 stituent parts of the blood, and produce several 
 acids, alkalies and earths, which were either not 
 found in the blood before, or existed in it only in a 
 smaller quantity, Thus, for instance, I found in 
 the urine a considerable quantity of sulphuric and 
 phosphoric acid, the former of which is not dis- 
 cernible in the blood, and the latter only in a 
 very minute quantity. The portion of earthy 
 and alkaline salts, which urine contains, is also 
 very considerable, whereas in the blood it is but 
 small. The different sediments, which the urine 
 precipitates whilst cooling-, I found to be either 
 solely the mucus of the bladder, which is always 
 present in urine, partly suspended, and partly dis- 
 solved, or a combination of this mucus with the 
 uric acid ; but it does ^ot contain earthy phos- 
 phates. I have endeavoured to show the neces- 
 sity of making a distinction between the me- 
 chanical sediment, which is abundant in the ca- 
 tarrhus vesicse, and comes from the bladder, and 
 that, which takes place when the bone-eartk is 
 
101 
 
 precipitated in the secretion of the urine, for want 
 4>f a sufficient quantity of acid to dissolve it. The 
 urea, which my predecessors had described, I 
 found to be a composition of the urea, properly 
 so called, and several deliquescent substances, 
 which they had not succeeded in separating from 
 it. The urea, such as I obtained it in my expe- 
 riments, is void of colour, and forms very distinct 
 prismatic crystals like nitre. It is, however, 
 very obstinately combined with lactic acid, lac- 
 tate of ammonia, ^and the above mentioned ani- 
 mal matter, which always accompanies this acid 
 and its salts, and which probably is also always 
 formed at the same time with them. This ani- 
 mal matter has a brownish yellow colour, and in 
 combination with the lactic acid and its salts 
 gives to the urine its colour. It is easily dis- 
 solved both by alcohol and water, and from this 
 substance, and not from albumen, as was for- 
 merly supposed, arises the precipitate, thrown 
 down from urine by tanning. The matter, which 
 in urine precipitates corrosive sublimate, is not 
 only albumen (the presence of which in case of 
 disease is very probable) but also a peculiar ani- 
 mal matter, which is not dissolved by alcohol, but 
 which, like that soluble in alcohol, always ac- 
 companies the lactic acid and its salts. It is not 
 
 3 
 
102 
 
 precipitated from the urine of persons in health 
 as long* as it contains free acid, and the want of 
 acid has, perhaps, some share in the precipita- 
 tion, which the sublimate produces in the urine 
 of persons in a feverish state. Besides these ani-, 
 mal matters, the properties of which my prede- 
 cessors had failed to discover, I also found a 
 mineral substance, which had been overlooked 
 by them, viz. silica. This earth is met with 
 in urine, and probably in all the fluids of 
 the body, though in very small quantities, and 
 has been introduced with the water, which we 
 use partly in the preparation of our food, and 
 partly as a daily beverage, and since no processes 
 occur in the body, capable of separating it, it 
 must accompany the fluids until it be evacuated 
 ty the excretions. 
 
 The diseased alteration in the urine, which ge- 
 nerates saccharine matter instead of urea, and 
 which was so fully examined by CRUIKSHANK, 
 has since been still further investigated by NICO- 
 LAS, SORG, THENARD, BOSTOCK, &c. Then- 
 analyses vary as to the results, and show, that this 
 diseased state is not always of the same nature; 
 but they all agree, that the new-formed sugar is 
 very easily destroyed during the experiments! 
 
103 
 
 and that it cannot be discovered in the blood* 
 1 have had an opportunity of examining" diabetic 
 urine, in which no sugar could be discovered, 
 and in which, nevertheless, no urea was fouud. 
 When alcohol was poured on this urine, when it 
 had been gently evaporated, it dissolved a brown 
 substance, which, after the alcohol was evapo- 
 rated by heat, left a quantity of stiff extract, in 
 which lactic acid was discovered, and together 
 with it some signs of lactate and muriate of ammo- 
 nia; the extract, however, consisted almost en- 
 tirely of the animal matter, which accompanies 
 the lactates, it was precipitated by tanning matter, 
 and left after combustion a small quantity of mu- 
 riate of soda, which had some slight traces of a 
 free alkali. 
 
 The urine of various kinds of animals has been 
 examined by ROUELLE, FOURCROY, VAUQUE- 
 ULN, BRANDE, CHEVREUJL, &c. and to these 
 experiments may also be added the analyses 
 made by FOURCROY, VAUUUELIN and KLA- 
 PROTH, of a collection of the excrements of a 
 bird from the South sea, called Guano, in which 
 they found a great quantity of uric acid, BRANDE 
 thinks, that he has discovered the same in the 
 urine of the camel, and YAUQFEUN found it in 
 
104 
 
 the stone from the bladder of a tortoise ; from 
 which it appears, that man is not the only animal 
 in whose body this acid is generated. 
 
 The Kidneys, in which the urine is formed, 
 have not been examined, and the chemical proper- 
 ties of their parenchyma are not known. The uri~ 
 nary bladder and its channels are similar in their 
 composition to the intestines ; but the mucus of 
 the bladder, such as it is deposited with the urine, 
 is very unlike the mucus in other places. It is 
 almost completely pellucid, forming 1 small grains, 
 which, when gathered on a filter, leave a slip- 
 pery and colourless mucus, which, however, often 
 becomes red in drying, and shows signs of con- 
 taining uric acid. After being moistened with 
 water it does not aofain become viscid. 
 
 The concretions, which are formed in the urine, 
 have, from the remotest times, been the object of 
 conjectures and experiments. From GALEN to 
 PARACELSUS, the ideas relative to these concre- 
 tions were absurd. VAN HELMONT compared 
 them to tartar; and after him, they were vari- 
 ously described by a great number, among whom, 
 HALES, BOYLE, BOERHAAVE, and SLARE, de- 
 to be mentioned. At last, some calculi 
 
105 
 
 from the bladder became an object of investiga- 
 tion to our never-to-be forgotten SCHEELE. 
 lie soon discovered the uric acid, described its 
 properties, and as he found it in all healthy urine, 
 he concluded, that this acid was always the prin- 
 ripal constituent of these calculi. HENRY after- 
 wards extended our knowledge of this acid still 
 further, and SCHEELE has been followed in his 
 investigation by several others, such as AUSTIN, 
 WALKER, BRTJGNATEIXI, and PEARSON.-T- 
 At last, Dr, WOL.L.ASTON published, in the Phi- 
 losophical Transactions for 1797, his analysis of 
 gouty and urinary concretions, which he proved 
 to be of four principal kinds, viz. such as con- 
 sist of uric acid, of double phosphate of mag- 
 nesia and ammonia, of oxalate of lime, and of 
 phosphate of lime ; and he gave at the same time 
 a short description of their external form, and 
 characters. In the year 1800, or three years 
 after WOLLASTON, FOURCROY and VAuatiE- 
 LIN published a more comprehensive work on 
 these concretions, in which WOIXASTON'S dis- 
 coveries were confirmed, but without his being 
 mentioned either in that work, or inFouRCROY's 
 Syst. des Connoissances Chymiques, among those 
 who had laboured in that field. But, notwith- 
 standing this omission, to WOLLASTON the ho- 
 
106 
 
 nouf is due of having been the first to discover 
 the different constituent parts of these concre- 
 tions; however, as the French Chemists had 
 near 600 different stones to analyse, and before 
 the work was published, had an opportunity 
 of comparing- it with WOL,:LASTON T S, it does 
 contain very important additions, and presents 
 us with a number of different modifications of 
 these substances in the composition of stones. 
 Besides the constituents, which WOIXASTON 
 had discovered, they found two others, viz* urate 
 of ammonia, and silica, the latter of which wa^s 
 only found in two instances; and the former, 
 BRANDE has lately endeavoured to prove to be 
 nothing else than uric acid united to urea ; but I 
 cannot consider his reasons for this opinion as 
 completely satisfactory. FOURCROY and VAIN 
 QUELIN tried, whether it might not be possible 
 to remove the stone without an operation, by in- 
 jecting into the bladder either very dilute acids 
 or alkalies, accordingly as the stone consisted of 
 uric acid or earthy salts ; but I do not know that 
 this experiment has been attended with any suc- 
 cess. They also tried to discover the circum- 
 stances, which gave rise to the generation of cal- 
 culi from urine; this, however, still remains a 
 secret, and we know no more about it, than what 
 
107 
 
 a long medical -practice has taught us, respect- 
 ing the more or less noxious effect of the diet of 
 the Patient. It was accidentally discovered, that 
 the alkalies, when taken inwardly, had a good 
 effect in relieving the pain, in cases of the stone, 
 and that vegetable acids aggravated them when- 
 ever the calculi consisted of uric acid ; but, not-^ 
 withstanding this experience, it is often impos- 
 sible to diminish the acid of the urine by the use 
 of alkali in those that suffer from an excess of 
 uric acid ; and I have myself tried in vain the 
 effect of acids in neutralising or acidulating an 
 alkaline urine. A middle-aged man was laid up 
 with the gout, his urine was foul and alkaline, 
 holding the earthy phosphates suspended in an 
 undissolved state. I gave him the sulphuric acid, 
 without any change ; and afterwards the ptys- 
 phoric, without any effect, until its dose was so 
 much increased that it became laxative : the 
 urine then became acid, and deposited uric acid 
 as long as the laxative effect continued, but no 
 longer, although the dose of the acid remained 
 unaltered ; lastly, I tried the acetic acid with as 
 little success, 
 
 BRANDE has lately attempted to prove the 
 inefficacy of alkalies as a remedy, in cases of cal- 
 culi formed of uric acid. DR. HENRY, who had 
 
108 
 
 found that alkaline urates do not precipitate 
 riat of magnesia, which earth consequently pro-? 
 duces with this acid a salt easily soluble, pro- 
 posed that an experiment should be made with 
 magnesia ; which experiment, according to 
 BRANDE'S statement, completely succeeded, so 
 that after using, for two w r eeks, from fifteen to 
 twenty grains of magnesia, morning and evening, 
 all the superfluous uric acid was removed, and 
 the patient became completely cured. This dis- 
 covery is as yet too recent to be considered as 
 sufficiently confirmed by experience*. 
 
 * Dr. Wollaston has described, in the Philosophical trans- 
 actions for 1810, a rare species of calculus, containing a sub- 
 stance to "which he has given the name of the cystic oxyd. 
 These calcali are in the form of a mass " confusedly crystalli- 
 zed," yellowish, and semitransparent : they are insoluble in 
 alcohol, and in the acetic, tartaric, and citric acids, nor are they 
 affected by the saturated carbonate of ammonia : but they are 
 dissolved by the stronger acids and alkalis : with the acids they 
 afford slender spicular crystals, radiating from a centre ; with the 
 alkalis small granular crystals ; and their peculiar substance 
 seems to be exhibited alone in the form of hexagonal plates, 
 when slowly precipated from a solution in pot-ash, by distilled 
 vinegar. Dr. Wollaston finds a greater quantity of uric acid in 
 the dung of birds, in proportion as they feed more on animal 
 food ; and hence suggests, that the tendency to deposit the uric 
 calculus, or to form gouty concretions, might very possibly be 
 obviated by a vegetable diet. T. Y. 
 
109 
 
 Of the processes, connected with the propaga- 
 tion of animals, and the matters by which they 
 are influenced, we know, as yet, but very lit- 
 tle. The seminal liquor has been examined by 
 VAUQIIEJLIN. Its composition begins to change 
 immediately after emission: it deposits by de- 
 grees earthy phosphate, which probably results 
 from its decomposition. Its characteristic con- 
 stituent, which in the first moment appears to be 
 mucus, becomes, when out of the body, thin and 
 liquid in all kinds of gas, and even in a vacuum ; 
 the humour, which in the beginning was alka- 
 line, becomes acid by degrees. Of the seminal 
 liquor of other animals, we know only the soft roe 
 of fishes, by means of the experiments of FOUR- 
 CROY and VAUUUELIN; and in that a peculiarly 
 remarkable substance occurs, which is insoluble 
 in water and spirits ; on being distilled in close 
 vessels it produces phosphorus, which is partly 
 sublimed, and partly dissolved in the empyreu- 
 matic oil. The substance itself contains neither 
 
 free phosphoric acid nor any phosphate. 
 
 i 
 
 The substances in the female, on which the se- 
 miiial liquor operates, are entirely unknown, and 
 the chemical nature of these processes is as 
 completely concealed from us, as the intimate 
 
110 
 
 economy of all other processes in Animal Che- 
 mistry. The phenomena, under which the fcf- 
 tus is formed and grows, belong- more properly 
 to Anatomical than to Chemical Physiology. 
 Even the manner in which the foetus receives its 
 sustenance and increase is perfectly enigmatical, 
 since we know with certainty, that the blood- 
 vessels of the foetus have no immediate con- 
 nexion with those of the mother. 
 
 The fluid by which the feet us is surrounded in 
 the womb, and, which is discharged at the birth, 
 has been examined by VAUCIUELIN and Bu- 
 KIVA ; and according to their analysis, the liquor 
 amnii in women seems to have a great analogy 
 with the fluid of serous membranes, and with the 
 humours of the eye : it contains no more than 
 from II to 1 1 p. c. of solid matter. In several 
 of the mammalia urine is formed in the kid- 
 neys of the foetus, and is carried off, through 
 what has been termed the urachus, into a peculiar 
 reservoir, which is formed by the allantoid mem- 
 brane. When the foetus is born, the urine 
 mixes itself with the liquor amnii, from which 
 circumstance it was long supposed, thatrthe dif- 
 ference, for instance, between the liquor amnii 
 of a woman and that of a cow, was very consi- 
 
Ill 
 
 cierable. DE Z'ONDI has, however, lately shown, 
 that these differences relate, properly speaking, 
 only to the urine of the foetus, which is contained 
 in the allantoid membrane. YATJCITJELIN and 
 BUNIVA, who examined these mixed humours, 
 found in them a peculiar cristallizable acid, 
 scarcely soluble, which they called amnic acid. 
 It greatly resembles the benzoic acid, but differs 
 from it in this respect, that it is destroyed both 
 by distillation and by the nitric acid. They also 
 found in it a peculiar brown substance, resem- 
 bling an extract, which is soluble in alcohol, 
 cannot be precipitated by tanning, and which, 
 consequently, is unlike other animal matters of 
 the same kind- Meconium has only been ex- 
 amined by BAYEN, and seems to be a biliary mat- 
 ter, converted into resin, the properties of which 
 the more resemble the bilious matter in the intes- 
 tines of full-grown persons, the further it has ad- 
 vance from the gall-bladder of the foetus towards 
 the rectum. 
 
 The Milk was first examined by BOYLE; 
 after him, BOERHAAVE gave an explicit analysis 
 of it. HOFFMAN, MACCIUER, and SPIELMAN, 
 followed; and lastly, ROUEIXE and SCHEELE 
 investigated the salts and other less-known con- 
 
112 
 
 stituent parts of milk. SCHEELE now discovered 
 the saccholactic acid and the lactic acid, and de-< 
 moiistrated several chemical properties of the 
 milk. A considerable time afterwards, milk 
 and lactic acid were examined by BOUILLON- 
 LAGRANGE and by THENABD, who declared 
 the acid to be the acetic, united with a peculiar 
 animal matter, from which it could not be sepa- 
 rated by distillation. FOXTRCROY and VAUQUE- 
 LIN gave us after this an ample analysis of milk, 
 in which they still further rejected SCHEELE'S 
 lactic acid, because its salts, when distilled with 
 sulphuric acid, produced an empyreumatic acetic 
 acid ; but as this is the case with several other 
 fixed vegetable acids, which still are not con- 
 sidered as acetic acid, the arguments of the 
 French Chemists seemed not satisfactory. 1 
 have* myself, also endeavoured to ascertain the 
 composition of this substance, and have obtained 
 results, which had escaped the attention of my 
 predecessors. I have proved that, in the forma- 
 tion of butter, air is absorbed, and not disen- 
 gaged, as some Chemists assert, this disengage- 
 ment only taking place, when the milk is in & 
 fermenting state, and has become impregnated 
 with carbonic acid gas. I have further proved, 
 that cheese occurs dissolved in the milk in a 
 
113 
 
 clear solution, and not merely suspended in an 
 emulsion, and I have endeavoured to ascertain in 
 what it differs from albumen, which it otherwise 
 resembles, and with which SCHEELE compared 
 it. I have also proved, that milk does not con- 
 tain gelatine; and that the extractive matter, 
 which gives a brown colour to the sugar of milk, 
 resembles what occurs in the humours of the 
 muscular parts and in urine, and consists of lac- 
 tic acid, and alkaline muriates and lactates, toge- 
 ther with the extractive animal matter, which is 
 soluble in alcohol. I have examined the greater 
 part of the lactates, and have proved, as I hope, 
 beyond contradiction, that the acid cannot be 
 either the acetic, or any other vegetable acid, 
 but is a peculiar and very remarkable acid, 
 which occurs in the economy of the animal body, 
 and for which I have retained the name of lactic 
 acid, which it received from its discoverer, al- 
 though it is found in greater or less quantity, as 
 well in the juices of the muscular flesh, as in urine ; 
 and I have thereby restored to our illustrious coun- 
 tryman SCHEELE, the singular honour of never 
 having advanced an erroneous statement relating 
 to the Science of Chemistry. 
 
114 
 
 Finally, with regard to the manner in which I 
 have endeavoured to treat the subject of Animal 
 Chemistry, it has been altogether different from 
 that of my predecessors, who, considering it as a 
 part of general chemical knowledge, have all di- 
 vided the productions of the animal body into cei% 
 tain classes, and described them only as objects of 
 analytical chemistry, to which they have added an 
 appendix, with some general reflections on the 
 economy of animal life. But this mode of treat^ 
 ing Animal Chemistry is altogether without an 
 object, and gives to the results of chemical in- 
 vestigations, little more than a technical value, 
 which, however, is entirely foreign to Animal 
 Chemistry, properly so called. For my part, I 
 have endeavoured to unite chemical and ana-, 
 tomical researches in the pursuit of one common 
 object, in order thus to give to the investigation 
 of the Animal Chemist, a determined and scien^ 
 tific tendency, and to his efforts, a physiological 
 view. As my predecessors have not always be- 
 gun from the same point, or taken their aim in 
 the same direction, it has happened, that much 
 has been overlooked by them, which might have 
 been found without difficulty, and thereby I have 
 been enabled, in the experiments which I have 
 
115 
 
 had an opportunity of instituting, to discover or 
 prove many circumstances, till then either un- 
 known or imperfectly stated, but of importance 
 to the physiologist : and I foresee, with pleasure, 
 that, when more able men than myself shall 
 hereafter occupy themselves with researches in 
 Animal Chemistry, in the same manner as I have 
 done, this interesting Science will acquire a de- 
 gree of perfection, which, at present, we not only 
 do not expect, but scarcely even venture to 
 hope, 
 
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Medical Books published by J. Callow. 7 
 
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Medical Books published by J. Callow. 11 
 
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