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With Plate XXXIII. figs. 1 to 6. >■ AFTER the completion of ray studies on the termination of nerves in the cutaneous epithelium of the tadpole, I began investigations on the distribution and arrangement of nerves in other organs, and have now arrived at what I consider important results, more especially in the case of liver. That of man was first employed at the outset of the investigation, but I soon perceived that on account of the small size of the cells here I would have to resort to some other Vertebrate for control pur- poses ; not that the liver of Man does not yield definite results, but that these might always be open to doubt if taken alone. Fortunately at that time there were a number of Necturi in the Laboratory Aquarium, and to these I resorted, on the advice of Professor Wright, obtaining from them my most valuable preparations of the liver. The hepatic cells in these are Trom two to four times in diameter those in man. It ^ obvious, therefore, that for ascertaining the relations of nerves to the hepatic cells the liver of Necturus (=Menobranchus) is tne most favorable that can be at the disposal of any hiatologist. I made preparations also from the livers of the dog, rabbit, and frog, which turned out to be of but indifferent value, and recognising that the narrower the field of inve.;tigation is ths more could attention be bestowed on the necessary details of technical manipulation and of observation, I devoted ueaily the whole of my time to winning successful results from the livers vol.. XXVII, PART 4 —NEW 8ER. » ' < •-« t4U A. P. MACALLUM. of man and Ncc turns. There is besides another justification for narrowing the range of the work as I have done, namely, that one of the highest and one of the lowest Vertebrate types are embraced in the investigation. I do not wish to be understood as believing that the results which I here advance are typical of every Vertebrate liver. Indeed, the following pages show a not very close agreement of results from the two types, and it would be hazardous to say which presents the form of nerve termination which has the most general occurrence in other Vertebrate livers. I may be allowed to insist on one point about which the vaguest opinions are allowed to pass currently as correct : the hepatic cell and nerve-tissue are in close connection, not merely by contact, but by actual union. The literature on this subject, what little there is, is full of contradictions or negative statements. Pfliiger, the first observer in this line, came to definite conclusions, it is true, but although experimental physiology has partially confinucd his view, taken as a whole and not in detail, yet the workers since that time who have published descriptions of their researches on the nerves of the liver have found no such connection between these and the hepatic cells as he describes, or, in fact, none at all. The reason for these contradictory results partly is that in nearly every case the researches were based on the Mamma- lian liver, the cellular constituents of which are too small to admit of de" itely deciding so difficult a question. I proceed now to give a resume of the literature on the sub- ject, coupled with a description of the methods employed in each case. A reference to these methods is necessary in order that I may briefly outline their advantages and disadvantages. Pfliiger^ used osmic acid to determine the course of the nerves. He found them rarely single, often in bundles, each single fibre dividing frequently and anastomosing, and finally penetrating the membrane of the liver-cells in order to termi- nate in the latter. The fibres retain their myeline investment up to the point of penetrating the cell. The fibres in the ' ' Archiv fiir die ges. Physiologie,' ii, 1869, also 1871. "TERMINATION OF NERVES IN THE LIVER. Ill interior of the cell terminate in a serins of fine fibrils with regularly placed granules or swellings along the course of eaeli. Heriugi found a rich supply of nerve-fibres entering the portal canal and branching with the vessels running in Glisson's capsule. Only a few were meduUated, the finest bundles con- taining only non-tnedullated fibrils. Ilering was unable to trace any 'lerves into the hepatic lobules. Ncsterowsky- injected the vessels of the cat and dog with coloured glue, and left sections of the organ so treated in a | per cent, solution of gold chloride for twenty to twenty-five niluutes, after which he put them in a weak solution of glyce- rine acidified with acetic acid, till they took a violet colour, which usually happened in five to fifteen days. In some cases he added a little of a solution of ammonium sulphide in order to bring out the nerves more prominently. He found branches of the portal vein surrounded by a ple\us of coarse and fine nc- ve-fibres. Out of the coarser plexus arise fine anastomosing fibres, forming loops ; they enter the lobules and closely twine about the blood-capillaries. Nesterowsky never observed even a connection between these nerve-fibres and the hepatic cells. He could not determine whether the nerves were meduUated or not, although he thought he saw in one case examples of the former. Kupffer'^ followed Nesterowsky's methods, and came to the conclusion that the fibres considered by the latter as nerves are simply those of connective tissue. He treated sections of the liver obtained by means of a Valentine knife with weak chromic acid solution (005 per cent.) and then left them for several days in a 0-01 per cent, solution of gold chloride, when they attained a red or violet colour. By means of this method he demonstrated the so-called " stellate cells," and at the same time found that the tissues immediately about the central vein of the lobule acquired a violet tint, a fact which indicated, he first thought, the presence of nerve-fibres, but he afterwards ' ' Strieker's Ilaadbucli,' p. 452, Leipzig, 1S71. ^ " Ueber die Nerveu der Leber," ' Virchow's Archiv,' Bd. 03, p. 412, 1S?5. ' " Ueber Steriizellea der Leber," ' Areli. fiir Mikr. Anat.,' Bd. xii, p. 353. 1*2 A. R. MAOALr-UM, considered the structures in question to belong to connective tissue, since they acted towards a solution of nickel oxide in ammonia liite the latter, and as he found the same sort of fibrils directly entering the lobules from the hepatic serosa. Kolatsehewskyi used t.To methods. In one, fine sections of the liver were pencilled out and treated for ten to twenty minutes with ^— i per cent, solution of gold chloride; these, put in water acidified with acetic acid, were left there for one or two weeks exposed to the light until they became coloured rose violet. According to the other method, sections of liver hardened ^^^^ TiT — rV Pei" cent, solution of ammonium bichromate were pencilled out and placed in a solution of the double chloride of gold and sodium of the strength recommended by Gerlach. The reduction is accomplished as in the first method , By these methods he found deeply coloured fibres running in the interlobu- lar spaces and entwining ultimately about the capillaries of the lobules. Some of the fibrils end in the nuclei on the capillary walls. The fibres branch, enter into the depth of the lobules', and form there plexuses of fibrils running parallel to and around the vascular channels. The smaller the capillaries the narrower are the meshes of the plexus. Kolatschewsky was not certain that these fibres are nerves, and he never saw their connection with the hepatic cells, if such occurred. His results agree in the main with those of Nesterowsky. Holbrook- made sections of the fresh liver when it was frozen, which he left in a i per cent, solution of gold chloride for thirty to forty minutes. The reduction of the gold was accomplished with formic acid. In some cases he hardened the tissue first of all with chromic acid, and then used the foregoing method. He found the nerves in the portal canal provided with a large number of nuclei and occurring usually in bundles of from three to five fibres, which enter the lobules and branch at acute angles along the capillary channels. The finest uerve-fibrill» ' « Beitrage zur Histologic der Leber," 'Arch, fiir Mikr. Auat.,' BJ. xiii p. 415. ' ■ ] " '!'i:t'^"'°'"^"°° °f Nerves in the Liver." ' Proceedings American So- ciety of Microscopists,' p. 95, 1882. TERMFNATION OP NERVES IN TME LIVER. 4i3 arc found rumiing aro-iiul the capillaries between these ami the hepatic cells. They touch, pass between, but do not enter the latter as PHuger maintains. Holbrook asserts that the fibrils are connected^with the cement substance or protoplasmic bridges between the cells, and thereby with the outer portion of the cell reticulum. He also corroborates the results of Nesterowsky's researches. Methods. To demonstrate nerve-structures in the liver of Nccturus the method employed was as follows : Pieces of the liver were hardened for a week or more in Erlicki's fluid, or for several days in a ,' J per cent, solution of chromic acid. After the hardening was sufficiently completed in alcohol, sections of the frozen tissue were made with a Cathcart microtome. These, when the gum was carefully removed, were put in a weak solu- tion of formic acid (5 per cent.) for an hour, transferred to a 1 per cent, solution of gold chloride for about twenty minutes, then washed in distilled water, and the gold afterwards reduced in the dark with a 10 per cent, solution of furraic acid. About thirty hours sufficed for this reduction when the temperature of the room was U0° C. The sections then had a deep red colour, but sometimes the tinge was violet. The chromatine of the nuclei of the hepatic cells took a deep blue violet tint, the caryoplasma light violet, while the cytoplasma came out very distinct as a mesliwork with a pink or light carmine colour. The nerve-fibres appeared deep violet, but the connective tissue of the interlobular spaces attained a light red, sometimes a deep red colour. ^Vhen chromic acid was used as a hardening reagent the addition of any organic acid at the same time, such as aceiic acid more especially, seemed to me to have the effect of robbing the nerve-fibres of their selective capacity for gold, while it increased the effect of the latter on the remaining constituents of the liver. I do net know whether chromic acid or Erlicki's fluid offers in the method described more advantages. If there is any advantage at all it is to be obtained from the former reagent. 4U A. n. MACALLUM. as With it one h apt to get beautiful preparations of ih. v which the gall-capiilaries, gall-ductst noTn"''" nerve, and the Cc.ent, of l^^U^^^ s ^T r' T' are demonstrated in a wav that I LJe\ "'"'•*'' other method of -anipull ^^^,' ^^ r,"/ ;^-.''^'' .\y - gold chloride in this respect I sh 1 re " '^''"^°""'' "^"' '^"^ quent paper. ^^"^ *° "S*"'- '» « subsc half .ho av.a.e'ir.t^r'".-,;;,;:;;:^-'-;"" "'"■« '- •"- In tl.e case of the h„„.„ |i,„ ,h,,„^j ;, .-oa^unt used in liardcnin,. The ,oc:lini^.J ""'•"' paraffl,, ,„e.!,„,l, a,„l were ,ub,e,„e„ ' !! T,"^ """'? "'"' "'» already outlined I found ,l„f " , '' '" "'" """'"" .Mn,e'etio„,did„o' t?« I ,1 Cin,^ "''' ," ""'^°™'-' l>ieoe, of nerve.fibres or fibrilleo; Id ,' """ '"" ''•-" ob,enred by the .bieknc, of he.e io '7' °' V'" "'"^ .ectmn, r,bout half an inch l„7'Z- J "T«"' "">'"»"' one edge .wo .0 three tin,: ^rZl'^nTj':]' ' ""'=^"» " •0 thai the thiekness decreased .-adVarf "''""""^ O""' other. With these sectio„rr «" ,"""•' f"" one edge to the in it. full exten ogeTr i hT T' '° "" "" '°"°» » «'« .hereby gained ail the advan a!e „f IhT °^'"•="-l>l«'. "d ;i.^.He faults of neither .oCs^^aX":' ::;;:-::: "rCdfttr "trstr.^ '- aiiT„:r;„:cr wben treated under e,acr iU S'"""" <"'''•' "' '""■ dishes, proved to be no. ! ""'' •"" '" ''i«''="^n ftre...o^o:« s . Xv,T:i7r'i-r' "*« »^•'■• of . very etrong colouring^ the ^old "• '" "" '''" the .tructure, fused a ! per cent ,«!, T"" " '° "'"""'•o .> recommended by CyfmltvT I y "'.1! r'"'" °'""''"' -..on i„ .his so,u.,-on .he proper ':>,^;:!7^:jT;;:Zl 1 ..> TERMINATION OP NERVES iN THE MVER. 445 by the solution of the execs, of t'ac fixed golil, this process of course being carefully watched. In this reagent one finals an additional advantage; the -rrve-fibres are the last to ,,art with the violet colour, thus ulng distinguished from connec- tive-tissue fibres. It, however, does not always operate m the latter wav satisfpctorily. The Hcctious of the hnraau liver received from the gold a dull violet or a dull red tint, while in other preparations u blue violet tirt was found. In two cases I obtained preparations whi'^ti to the eye appeared almost colourless, but which on cxa.jination demonstrated the nerve-fibres very distinctly. All the sections were cleared in oil of cloves, and mounted in balsam. , . _ In the study of the ulti.Tiate terminations of th3 nerves 1 have used the Lcitz j\ inch homogeneous immersion with special illumination. In the human liver, more "specially, it was impossible to do anythini wich a less eEScient objective. In the Nec*urus liver it was quite easy, however, to see the required struoturcs with a system 7 of Leitz, but I have endeavoured in every case to verify my observations with the higwer power objective. The value of gold chloride as a reagent for differentiating nerves is not admitted by all histologists. It has been urged also that the elements it selects in a fresh tissue and those it differentiates in a tissue hardened by a reagent such as chromic acid are not necessarily tht same structures. This objection has a great deal of force, especially in view of the fact that gold chloride gives a violet tint to connective tissue v;hich has been first hardened witli chromic acid ; the corium of N ecturus and the connective tissue around arteries are cases in point. More- over, the tendency of a hardened tissue is to reduce equally the gold so as to give to all the tissue elements a violet colour. \ et with all its faults the method of hardening with chromic acid and the subsequent treatment with gold chloride has many advantages over o*her micro- ch.rnical and staining reagents, and so far as t'iC demonstration by It of Lerve-structurcs arc concerned no greater suspicion should be atti ^hed to results lt^^~^i 446 C- MACALLUM. nerve-structures, for these have 7X "1 '" '"'^"''^'^ ''^' ^^r their intrinsic for. anTarr ^ ^ t^^^^^t'^'^^^^'"'"^^ ^^ termination, or either se .aratehf T. ' ^, *''"'' °"°''^ a«d gold chloride to fibres othCi^f ''d '"^'? '°^°"^ «"^^^» ^y accessory value only. ""demonstrable is therefore of It is not known definitely to - I nf the capacity of nerve-fibres for fix'i.^ 17^'' .'^"'"P^'^^d is due R. Gscheidlen,! after a seres of ' '"''^''^ ^"^'^ ^^^'^ride. -aclnsion that the reduction scauTedT"';' ""^ ^° *^« He reated pieces of the ischiadic nee J \ '' '"''''''''''- alcohol, and water respectively and I / u"^ ^^'^ ''^'^' obtained with ether reduces gold L IT f '' *^^ ^^^^^^ obtained with alcohol took longer to do If '"' ^'^^'^ ^^^^^ extract, on the other hand, a Zl L ° ''T' *^^ ^'i"^""^ of the solid extract obtain d with eth! f ^' '^ P^'' «^«*- Gscneidlen drew the inferenJe h! " '"^ '"^ ''' "^t»re reduces the gold. I do not fi • . x^ '-'onstituent of this fat suffice, for nearly J .t ^^'J^^^ ^^ ^t this explanation ^H the myeline investment of the fit ' T '""'^ '^^'"^ ^om re action usually occurs in thrJdS "foI'^" '"' '''' ^ the violet colour may have another 1:. " ^°''"' °"' ^''^^ reduction of the gold and o.Vi / ^''P^^^ation than a mere «;-ted by Lindel th^Mhis tag^ f^ ^V^^ ^^^ Pernor phosphorus compounds, espee all v t , n' ^""^^^ ^^^*« "ith aqueous solutions of a'vioet "L mT'' "'"^'' ^•- undergoes reduction or enters into? ''"'' ^"^'^ chloride 't is outside the province of the 'lT"'"'°P^'^^*^d condition posnble, howeve., without tra 1 t/r' l' '^"^"^'^- ^^ i' aspects of this question and to IZ f '"' *° consider some help in the solution It seems f^^' .'"'"' P'^'"*^ ^hich nav favours the production IfTr;, ^lo ''' 'T ^"'^*^"- ^^^ diffusea through all forms of itu /d Tf' ^^^'^ '^''^^^-^ - coneentrated condition in nerveSu 1^' {\ ^' ^^"^ - « Arch fiirMikr. A„at./Bd.xfv p 22. * ''"*'«" of TERMINATION OF NERVES IN TUE LIVER. 44^ ■I liver be treated with gold chloride, and the process of colouration be watched, it will be found that the first tinge which the nerve-fibres take is red, and afterwards they show all stages transitional between that colour and violet, while the other systems of tissue slowly pass through the same order of colours to the violet tint. The nuclear chromatine is an exception, being, like nerve-tissue, quick to attain a violet tint. Occa- sionally other structures act like nerve-fibres towards gold, and among these may be mentioned certain paranuclear bodies in the cutaneous epithelium of Nectur us which are first coloured red, then rose violet, and finally deep violet. This appears to show that the substance which fixes the gold in a violet form is not confined to nerves, but is diflfused to a small degree in other tissue elements. The finest nerve-fibrils being hardly thicker or less delicate than the trabeculai of the cytoplasma, it is wrong to suppose that a reagent which does not specially preserve and fix the latter will do this for the former. It is in this respect that I find the reason for the failure of Nesterowsky, Kolatschewsky, and others to resolve the finer nerve terminations, seeing that the reagents they used for hardening the tissue do not render the cytoplasma distinct and firm, and with it the finer nerve- fibrils. Ammonium bichromate is not a suitable reagent for this purpose, neither is the weak solution of chromic acid such as Kupffer used. The same objection can be urged against the method of freezing the fresh liver in order to obtain sections. The method of gold colouration must not be allowed to injure the cytoplasma. The test which I always exacted of the method employed was the distinct demonstration of the cell reticulum ; that being in a good state of preservation, it was only a question of the number of trials with gold chloride in order to get the desired demonstration of the termination of the finest fibrils. I think also that the clearing up of fresh tissue with formic or acetic acid previous to steeping in gold chloride is apt to destroy both the cytoplasma and the finest nerve-fibrils. It is on this ground that I advocate the use of chromic acid to fix these before subjecting them to the action f 448 A- B. MACALLUM. of gold chloride ami t« +1, or acetic acids/ OsJic ti/lho"".* '"^^^^"^ ^^^ formic ™ed. 'ated ne.ve-fibres, iHnrJ^'re /^^^ " ^'^^ ^^ «f finest non-medullated fibrils ' demonstrating the He- a few words are ne'-cssarr . the cytophsma. I„ fig3 3 /t^.^^^^'-^'^g the structure of -ork with thickened n^dal 'poLus \V' Tr"^'''^ ^^ ^ »«t- 't does not alwavs appear i„' u h a r. T ""' '^""^"^^ ^^at "'eshes are often much lar^.r^.d V »" '^ ^''''angement. The droplets Often also the tTalCt thi ".'' '^""^^'^^ ^>' '^^ Phery of the cell, so as to b i ,! °" ^^"^'"^ *^'^ Peri- spec.mens of Necturus from T / '"'^'^*'»^»i«hable. The -de were caught ear"; ^mI c'b I «" ''''^'^'^^^ -- t ere was but a small amount of faj •',''', ^"^ -"-quentl, appearance presented in the . "^ '^^ ^''P^tic cells. The c'-omie acid material wu/helatrvr " ^ "°'-™^' -^' ^or similar arrangement. PlemmTn J bY • " "^ '"'"^ ^'^^^ ^^^O'^ a 0/ the cytoplasma in thread^T.f t '' '" '^' arrangement tl-se form a network ul a Klff"*/^'^ ^^^'> '^' ^o'ubts " however, like those drawn n it Tln'dT^- ''^"^*"-> doubt as to the occurrence of a r^^iculum ' '" '''''' ^^ In sectionslTth?."" " ''' ""^'^^^^ ^'^-«- vej^s take a rose-violet or blue v Ltt c f ^ "' ""*"^ coloured fields, observed with ao ! '^''"^ ^'^°"g'y consist wholly of violet-c J ured fib^T" "'j^^'"'^' ^^m'to "magnified the latter, which are com ', "' "^'" '"^^^ ^^g^^Iy -e seen to constitute but a TZT^VT^'' '" ^>-'les! t'-ue, or of that about the centra l u' *^' '^^crlobular the bundles a quantity of connedi ' ^'' '^""^ ^^^^^'^^ or red. The thickest fibres are nf . "' "^'^^''^d light violet ^ach bundle is eomposZ/t;-: Tf '"'"• '''^^^^ xWii. < 7 ., , , -"v'ug number of fil ''•'^'' •■"IS Journal, vol. TERMINATION OF NERVES IN TQE LIVER. 449 usually separated from its neighbour by a narrow interspace le.-s in diameter than that of the bundle. The fibres when seen in transverse section are round, and possess nuclei which are closely applied, sometimes at definite intervals. The fibres are wavy in their course, and are clear and homogeneous. They brancli frequently, the branches being c*" diminished size, round, and lacking the nuclei of the larger trunks. They appear in no way to be related to or derived from connective- tissue corpuscles, they do not anastomose with one another, and they nearly always have a parallel direction, decreasing in size as they pass into the smaller divisions of the interlobular canal, where their arrangement in bundles is not so common. The violet colour of the fibres render tliem remarkably distinct in contrast with the rose-violet connective tissue in which they lie scattered. Sometimes, however, the connective tissue is not coloured at all, but comes out as a granulo- fibrillar appearance which is apt to be overlooked in the presence of the deeply coloured fibres. In these cases the bundles are separated by the granulo-fibriilar substances which penetrates much less prominently between the individual fibres. Where connective tissue and nerve-^fibres are coloured alike, it is useful to differentiate between the two with the aid of a eak solution of potassic cyanide. The section being placed on the slide a drop or two of this reagent is added to it and the decolouration Avatched with a moderately high power. "When the interlobular tissue is deprived of its colour to the degree required the section is mounted in the usual way. Under the high pov "r one now finds only a portion of the interlobular tissue retains its violet tint, and this portion is composed of the fibres above referred to. This does not neces- sarily show that the fibres so revealed are nerve-fibres, or definitely distinguish them from those of connective tissue. It, however, seems to agree with the experience of Cybulsky, that in tissue stained with gold chloride, and subsequently treated with potassic cyanide, the nerve-fibres retain their colour longest. I 1 450 A. C. 5IACALLUM. I have never seen the connection nf ih ^,. lated nerves, having never foundtif ' ''' ^^''' ''''^' '""'"'- normal or abnorn.fl occur e/e o7 1] I •" ^''^ ^'^^''^ ^"^ ''- canals I do not doubt. Me^, ted ^^ ^b' "" ^"^^'•''''^"'- found ,„ unusual places. For ex mn? ^? ''' '°™^*'"«« meduliated nerve-fibre penetratL T^ '' ^^^"'^^^ ^°"»d a and I also have seen the'sa^e "h f. n' '"''""" '^''''^'^^'- ' 'o-a. One n.a, be inclined tSe"\rr''"'^ °' '^'''^■ Jated nerve-fibres can and do occur u^^'^T'"^^' '^'' '"^dul- remembered too that gold chlorl ^'''''- ^* ^« *« '^e den^onstrating the ^elineljt'Zrl ' '''''' '-»-^- ^or renee of which may escape thnl °^ ""'''''' '^'^ °ccur. wiih the one method. ^' ''^ Preparations obtained It is quite true as !<:„„«• violet-colo.ed tLl^;^: ^T^;^ ''''.'^ ^-^^ preparations covcnng of the liver between the hi'r '" /'°" *^^ ^^rous ^0- 1- statements that he "r/os sT: '''"'"^- ' ^^*^- J'e hepat.c tissue in this way sl, "° ""''''' ^«" ^each less, seeing that the serosa an^ 1 ^ '"PPos^tion is ground- oneandthesameori^n Ind on '"'"^^^"^'^^ ^^-"^ are of contain nerve-fibres.' Vhe';: " " '''''' '' ''' ^^^er to ^as coloured violet throughou iThw^?^'''''''"^ '^' ^^^osa 'on of potassic cyanide, and ound '^ ' '^°^ °^ ^^^ solu- te be true here which i hi T ."^ f "^^Quence the same canals, „an.ely, the prLen e" of H f '" ''' ^"^-^^^ular «-ve and connective,'the " '/ "' '^^^^^ °^ ^-^'^c- dominating. ^^"^r, however, very largely pre- ^^^:i firr::;fihTri'i^"r ''^ '""^^- ^^ ^-ge, 7 distinct, and is more r di v J \?' ''"''' ^°'°»'- - -« .^'-^ that of the large fibres utr''^'7^*'^P°*^««'«^^anide '-"e. I an. doubtful olhei^^^^^^^ jPParently answer to the U leTn ".I' °' *^^^^' ^"^ ^'-7 4uani]ty. The nerve-tissue is TRRMINATIOM OF NERVES IN Till'. LIVER. 451 found absent frequently in otherwise successful preparations, and the fibres usually are not more than half a dozen, each separated from the otlier by a considerable interval of space. For tracing the nerve-fibres further to their termination it is necessary to resort to the special sections which I have referred to, namely, those which decrease iu thickness from one edge to the opposite one. In a section of this sort, if the thick edge includes a longitudinal view of one of the interlobular canals, every facility is thereby afforded for following these fibres. A uniformly thin section is not of much value for this purpose, as in ic the fibres can be followed but a short distance, on the average equal to the combined diameter of four or five cells, and the connection of the smaller with the larger fibres is diffi- cult to make out. Part of a section prepared in the manner described is drawn in fig. 1, which represents the border of a hepatic lobule. At si'ch a point are found medium-sized fibres coloured deep violet, always with a clearly defined border, quite different in this respect from connective-tissue fibres. One sees them arise from the large deep violet fibres of the inter- lobular canals, often as a direct continuation, without branching until after they enter the lobule. They are not numerous, there being usually two of them to each capillary channel, and they run between the capillary wall and the hepatic cells. They are easily distinguished with a low power objective. At first view they appear to form a network of anastomosing fibres, but a further examination shows that the branches of these fibres cross rather than join each other. Fibres of such a diameter are never found outside the capillary channels, that is, they do not penetrate between the liver-cells, These fibres belong to what I have denominated the coarse intralobular plexus. They possess no nuclei and branch at acute angles, the resulting branches being either quite as large as the original trunks or much finer. The large ones may be considered as belonging to the plexus just mentioned. The finer may be resolved into two classes : a perivascular plexus or network and an intercellular one. The perivascular network can be best seea when cue looks from above into a capillary channel cut 452 li- MACALLUAf. JoiffitudinaUv greater or ies's in V^a' thrift '!f I ^rT' ''^••^ '"-g"'- and are very fine, without varico e Iwlir ^' ' ''"' ^"'^ ^^'^ A^^rils appeanng q„ite distinct ^a st "tn "' "'''^ ^ "«^^* ^"^t ground forn^ed bv the hepa „ '" 'r *'"* ^^ the back- \"! ^'^^^'t «°"tinuatio„ with the fib r''^^'^"^^^ P'«-^"« obu ar piexus, and is therel o ' , *^' ""^"^ ^"^-- ^ belongs .0 the Malls of the ca^l r"''."'^"'"^- ^^^^^^'^-r ^epataceells bordering on th se oT 7 ^^'""^^^ ^'^ *° ^l- Sometimes it appears fo beJon. 'o "nf ': ' ''^ "°* ^"«-- I cannot eve.i say whether If !" , ' '«°>^times to the other "^'-rk. The latte r L f„ T'. '"" *^^ intereelluTar commonly seen uneoz^n ^^d l," ,°' '"^ ''^^•'^^^ -"^h a e i-parations show anasto^TenT^"'"' ^"* '^^^-'' -go^^^ - end.ng between the hepa ,o ee Th' .' "^^"«" '''^^^ ^^ Po^'^ess varicosities regula Iv .rra ' / ? ^^^ °^'^'^^^ ^briis bo-ogeneous in:„,ersion le fses S" ?'"""'^^°"'.^ -''» All my efforts to find a Zn , ^ '^ '""''• Penjascular plexus ava led roth" ""r"" ''''' ^^riUottUe - Kolatschewsky found in one f T ' '""'" '^^'^-^ ^^g^*^ ""c^ez of the capillary wall but ..° 'T' '"''"'"^^^ "^ ^he ol^^ervations either for a nLti T *" ''"^ ^ ^^'^ '""ng no - -7 preparations the cap C wall T f '""''''' --' ^'-e ^7 gold chloride, appeare Xt 1 '"''.r^^^'' "^^--d l^val.ne refracting membrane The "'"'"t^"^ P"'^^'' ^« ^ a I have already pointed out serve ,'''''"^'^ ^^^^"^ '"-y, i^^^^"«- ' ''''" "' °"g'^ to the intercellular J'rom the fibrils of fi. • «es8ivelymi„ut,twiJ,: ^'^tercellular network ex- -,«,^ in a delicate :f XlV'' ^^^'^^^' ^"^-te cc^l« near the nucleus I„V.!t"^^^°^ «^ the hepatic 1 one often suspects such n ne"l "?"'' '^ *'"*^'^'^- ^^ ^S- ofl;omogeneousin.nersionob;S^^^^^^^^^^ but the use satisfactorily, and only a care^u T "?''^'"°"«^r-^c them ^7 ;> five or six cas'es r"ult Lt'^ ..1 "^^ *^^" «-^-- 'fed, in son.e specimens eeuer 1 ''"'^'"^- ^ ^^-^^^ colour passing fron, the capiCS^t/;^«b'i^^ of a violet' ^ rj side of the hepatic cell to the ;4 TEUMINATION OF NERVES IN THE LIVER. 453 neighbourhood of the nucleus and there end with the character- istic bead-like swelling; but I could not prove to my own satisfaction that they were other than prominently coloured trabecule of the cell reticulum. A view of a specimen such . I have represented in fig. 2 lends itself easily to interpretation. Here a fine nerve-fibril running along the side of the hepatic cylinder gives a fine twig to each cell which reaches the vicinity of the nucleus. Sometimes a twig divides after it enters the cell, the divisions running to opposite sides of the nucleus. The terminal points of all the intracellular twigs are delicate beads. I was always compelled to believe that such twigs are really within the cell when I found their terminal beads to be on the same level as the nucleus in an optical view of the latter. It is, of course, impossible in the greater number of cases to say whether the fibrils which give rise to these intracellular twigs belong to the perivascular or to the intercellular network. In fie. 2°oue finds great difficulty in determining to which network the nerve-fibril belongs, but in several cases the demonstration of the intercellular origin was quite distinct, and this has led me to conclude that only the intercellular fibrils give off intra- cellular twigs. The Nerves of the Liver in Necturus. Tue hepatic cells in Necturus measure 0-0i2— 005 mm., and consequently in a given area of a thin section the number of cells is less correspoudingly than in the human liver. From this one would expect to find a less rirli supply of nerve-fibres, and results bear out this opinion. The nerve-fibres in the interlobular canals are few in number, and each has a diameter much narrower than that of the larger ones of the human Uver ; their course is straighter till they enter the lobules, where they pass along the capillary channels to their termination. The small quantity of connective tissue ir the interlobular canals usually takes a deep violet stain and then appears homogeneous and structureless. In su ^h a case I have not found it necessary to remove the excess of the stain, for the nerve-fibreis are clearly outlined against the connective tissue. Apart from the larger 454 A. B. MAOALLUM. 1| .Dlorlobu arca-al, the connective tmne also is not demonstrated fi^bre^for a long d,s,anee, providing it lies in ,he plaL of the Nuclei were rarely observed on tlie largest fibres an,) ^I,„,l. tese be,o„.ed to .l,e sheath of the Sbr/or to rerVe— e" L V?r, '° ''"'""''"'■ •">= division of the fibre, in the .nterlobular canals is rot co™„,on, but branch „"olr° Z '"'•i"'""" '" ""> «Pi"»rics of the lohnles" Here they 6,ve nse to fibrils of two sorts; those which form tie STw in- n^r"'"""''"^ "■' '"""'"^ -lU an^h cellf '{Tn,'::a":et^?/SLrer i^"^" '"^ 'r'' or physiological difference^ bete'e: ttt lIL 7of"fiS°'°!^r ercellnlar bnis ari^e from fibres which serve as o Wns Jo rcayTarcdast'olr'^ ,""' ,"''^ ^"W""' ""= --'-■- r:rw;?r:i\re:'rc?ir.r'-'''-"^ outside the^apil.ar'^'Ih': n U ^l^Z:Z':TfL "' course. I have follnwprl +1, • greater part of their .o.he bin:d'^l^r:frt::nT:fXtrrdr found them to accommodate themselves but verv little 1 th' wmdmgs and tortuous course of the capillaries In hi! Observed to ^:t::::z^x^^:'t:::;r'' course is in the ranllo-^ „v, . • ^ , " "^'*"*- -t^artot their h.ood.capil,ary7nTScrt1'i;er!;r"'™ '"' "" "''"' form bituslt zir':: """^ ™^ "-^ - •- -0 cell and ofLTrS ^ ''ar , "''/."-«■' ^^ « "-epatic fibrils .hich form tS™ '""'''"'eular or triangular shape. The ' =~seeom;s-rh:™:rrrdr:t ^ - — 4 TERMINATION OF NERVES IN THE LIVER. 455 a longitudinal section of a capillary contains a view of this plexus in all its relations, on the one hand with the hepatic cells, and on the other with the capillary wall. The latter appears closely embraced by the network which al v vi well- preserved specimens, borders the hepatic cells. In tL.s respect one has great difficulty, as in the human liver, in deciding lo which the network belongs physiologically, if to the capillary wall or to the cells ; the terminations of this network show that it belongs to the latter. Is it to be supposed, however, that nerves are not distributed to the capillaries themselves ? It was of course much easier to determine how the long intercellular fibrik terminate than to do the same thing for the fibrils of the perivascular plexus. My first conclusion, after some observation, was that both terminate in a like manner, but I soon perceived that it was rarely possible in thin sections to decide whether a fibril which runs in the capillary channel and gives off intracellular twigs belongs to the intercellular class or to perivascular network. Both class of fibrils are equally delicate. The intercellular ones I found again and again to terminate within the hepatic cells. I had therefore to guard against confusing the two sets of fibrils as to their ter- minations. One of the several cases where an absolute decision was possible is drawn in fig. 3. Here fibrils of the network are seen to give oft" twigs which penetrate the adjoining hepatic cells, while on the opposite edge of the capillary channel a fibril, apparently belonging to the intercellular order, terminates in a like way. The intercellular fibrils branch at certain intervals, each branch running at sharp angles with the main trunk. I believe several times to have detected a network of these branchlets. In such a case these intercellular fibri's would correspond to those of the intercellular network in the human liver. I must, however, leave this point in abeyanc" If this network is usually present obstacles to its demons, ^tion are certainly to be found in the deep tinting which the cell reticulum acquires from the gold method. The perivascular network, on the other hand, is not obscured, for the capillary walls over against which VOL. XXVII, PART 4. NLW SER. K K 456 A. n. MACALLUM. It .« usually seen arc uucolouml, or nearly so. Tl.c fibrils of tho .ntcrcellular order are generally so delieatc that it is difficult o arrest the removal of the colour of the overlying or under- 1^7or r '''\\r'''''' ^^-^-^« «^ « 1-*"* where the distinc - try.ng o determine definitely the common occurrence of an intercellular network. ^urrcnce or an The simple intracellular nerve-twigs always termi nate ehe neighbourhood of the 'nucleus, ,?;; sing y or after branching, each terminal point be nJ a delicate bead. The unbranched twig may end on th! side the nucleus facing the point where The twi.pen tra the cell, or after curving around the nucleus on the opTos e or on one of the lateral sides. When a twig b ano^c two or more of the branchlets may terminate i^ the po stions mentioned. In many cases it is possible to trace a t2 wmmm fig. 4. A complicated mode of .ndin,r n ^^P^^^sented in on to iari , a 1 T°"' "''''^ ' '■"" '""' f-*" n.ode. Hire at. „d"7- , """'='^' " *''"' '''™ "■" °"-«r tratM a ..11 , u ■" "'" l'"i™'ral" network pene. eh „: aH trT ~"''™°'" "'" "" "='' -'-I- ^ belong to .l' 'mprcssion at first that thU reticulum Uelouga to the uervetwig rather than to the cell itaeK C TERMINATION OP NERVES IN THE LIVER. 457 opinion being at tiie same time strengthened by the fact that the cell network is coloured deep violet. The trabcculaj of the reticulum in such cases as this are very much more slender than they arc as ordinarily demonstrated, but au exception is to be made of cases like that in the figure, where the tiabcculte become thickened along two or more lines so as to j^ive the intracellular nerve-twig the appearance of a branching which extends toward the nucleus. In fig. 0, however, the reticulum is formed of trabecule nearly as coarse as that usually observ. 1 in the cell. The demonstration of the simple intracellular termination occurring in the same cell with the more complicated form is apparently not possible. The former, if such is present when the other mode of termination is demonstrated, must necessarily be obscured by deep violet colour of the cell reticulum ; if this depth of tint be lacking it is possible to see the simpler termi- nations. Both forms are often demonstrated in the same section, and therefore one cannot consider that the method of hardening previous to treatment with gold chloride may account for the presence of the one or the other on the ground of their being artificially produced. It is probable that every hepatic cell in Necturus presents both forms of termination ; otherwise we ought to conclude that there are two kinds of specifically different glandular cells in the liver according to the doctrine of the physiological homo- dynamy of nerves. The simpler form of termination may be regarded as the same as that found in tlie cutaneous epithelium of the tadpole,^ while the more complicated mode is apparently the glandular one. Lt present it is useless to discuss further the specific function of these, but I hope in a future paper on nerve terminations to treat more fully this aspect of the question. General. In the liver of Necturus there is a mode of nerve termina- t'on which I have been unable to demonstrate in the human ' This Journal, November, 1885, p. 53. 458 A. n. MACALLUM. liver. Ill this mode the ucrve Kbril (uses ur is co.itiimous with the reticulum, but the fibril first penctrttccs the cell in ord'>r to accomplish thiu fusion, and in this way differs from the method of termination descrbed by Holbrook by which the fibrils arc connected with the intercellular bridges or cement substance. 1 thou><;ht at times to see with oil ia.raersion objectives such u fusion of the nerve-fibrils with the cell reticulum in the human liver, but it was in every case impossible to obtain demonstra- tions as definite as those yielded by the liver of Necturus. This method of termination resembles to a certain extent that described by PHiigtr ; the resemblance would be a more complete ».ne were the cell reticulum regarded as of nervous origin, and then the words of that observer would be applicablp here also : " Man kcinnte demgemass sagen, dass die Lebcrzelle cine Kernhaltige Anschwellung eines Nerven sei." The points of difference between the method here described and that of Pfliiger's are, however, too many to permit the supposition that they are one and the same but viewed according to different modes of prepa- ration. When one compares the observations of Nesterovvsky, Kolatschewsky, and Holbrook on the extreme fineness oi' the nerve-fibrils so i^, .i: thjy could trace tbora, the termination of nieduUated i'.wr- ',\ t le hepat.v cells appears exceedingly improbable except in patlioiogical cases. Witii regard to the methods of technique employed by the other observers several oI jectious may be ur^ ed • ihese I have alread} put forward. The methods are no doubt useful in demonstrating the course bit not the termination of the nerves. It must be thoroughly understood that the nerve terminations in the interior of liver-cells are as delicate, as easily injured, and as difficult of demonstration as the finer cell structure. If thir, point is admitted I do not apprehend that a confirmation of the Jescription of the nerve terminations here given will be a tardy one. Of course there are reagents which preserve well the cell structure b .t wliich do not fix it in such a way as to permit the selective capacity of gold chloride full play, and one must then endeavour to find such reagents a.« will give with gold chloride the best results. I have found these in Erlicki's V . ..\. i TEHMINATION OF XEBVK8 IN THE MVEH. 459 Huid and cLromic acid, but it is possible thai by varying the methods of the fixation of the gold some other reagent for iiardcning will give better results thn.n I have obtaim d. In conclusion, I niuy state that I huvc dom in-iijitcd these terminatious to several competent observers, and among these 1 may racntiou Professor llamsay Wright and ' rofessor Osier. To the former I owe ray thanks for his having gDiic over and verified every point licrj advanced and for the advice of which I availed myself at /arious times during the rcscaich. I 460 A. B. MACALLUM. EXPLANATION OP PLATE XXXIII, figs. 1 t- 6, Illustrating Mr. A. B. Macallum's Paper on "The Termination of Nerves in the Liver." All the figures are representations, as exact as possible, of tbe structures drawn. Fig. 1.— a section of the edge of a lobule of the human liver to show the course of the nerve-Cbres. The clear spaces represent transverse and lon-i- tudmal sections of the radial capillaries where they are continuous with the interlobular capillaries, a. The coarse intralobular jilexus. 6. The perivas- cular plexus, c. The intercellular fibrils. A. The hepatic cells. The capil- lary walls are indistinguishable. So.ne of the larger uerve-fibres appear at places to run over the liver-cells, but at these points they actually follow the capillary pathways. Leitz. Oc. 3 and Obj. 7. The outlines of the cells, nuclei, and fibres were drawn with camera. Fig. 2.— Two cells of the human liver, showing the termination of ner/e- librils m their interior. Leitz. Oc. 3, and oil immersion j\ inch. Pig. 3.— Shows the simple intracellular termination of nerves in the liver- cehs ol Necturus. a. A larger nerve-fibre. L An intercellular fibril, with c, the perivascular plexus arising from a common fibre. Eriicki's fluid gold chloride, formic acid. Leitz, Oc. 3 and System 7. Fig. 4.-Shows the dendritic branching of a nerve-fibril in the interior of a single hepatic cell of Necturus. Eriicki's fluid, gold chloride, formic acid Leitz, Oc. 3 and System 7. The branching of the fibril in the interior 01 the cell was drawn with horn. imm. -^ inch. Fig. S.-Two hepatic cells of Necturus with ncrve-fibrils of the neri vascular plexus ; a fibril from the latter eaters each of the cells and becomes contmuous with the cell reticulum. Eriicki's fluid, gold chloride, formic lltcJrV^A '''•' "^/'f'- ""'■ '■ ""^ '^^'^"' ^■' b"^ '^'^ 'bourse of the fibrils outlined as seen under horn. imm. Jl jnch. Fig. G.-A single hepatic cell of Nectur Js, showing the relations of nerve- fibrils and the cell reticulum. The optical plane is above the nucleus and near the upper surface of the cell. The ncrvcfibril passes over the upper surLce of the cell, and gives off a branch which divides into twigs to penetrate the cell and fuse with its reticulum. Erlecki's fluid, gold chloride, formic acid Leitz, Oc. 3, and oil imm. -,V inch. 2^ii '*^^#-''^ NUCLEI OF MUSCLE-FIUKE IN XECTUJtUS LATERALIS. 1(J1 On the Nuclei of the Striated Muscle-Fibre in Necturus (Menobranchus) lateralis. By A. B. MacaSlum, B.A*, I'ellow of University College, Torouto, Cauada. With Plate XXXIII, figs. A aud B. While examiuiiig, several months ago, some preparations made for the purpose of demonstrating the mode of nerve termination in the striated rauscle-fibre of Necturus, I found many of the isolated nuclei to possess on their surface furrows and striations hitherto undescribed, and which, I now believe, are of importance in determining tlie structure of the contractile element of muscle-substance. A careful study of these nuclei has further revealed other peculiarities which point to a conclu- sion as to the origin of the contractile element, the muscle reticulum. In view of this, I give a detailed description of the appearances presented by the nuclei, and refer them to their supposed causes. The best preparations were obtained with gold chloride aud formic acid. This method is valuable for two reasons, the nuclei are completely isolated after a stay of thirty to forty hours in the acid, and the furrows on their surface take a deep violet tint, while the remaining portion of the nuclear membrane is coloured light, or rose violet. The isolation of the nuclei from the muscle- substance prevents any confusion which might be caused by the striation of the muscle-fibre were one to examine thjm in situ. It is to be noted that the muscle-fibre in ■ »■■ -'■^itr^.' 482 A. R. MACALLUM. Necturus macerates and disintegrates very easily iu solutions ot formic acid. The long diameter of the nuclei, the largest and the smallest, measuns 0037—0053 mm., and the transverse diameter 0010 — 0-025 mm. The form of the nucleus varies somewhat, the oval being the most common; oblong and quadrate ones were occa- sionally observed. The membranes of old nuclei Lave apparently the capacity for attracting the reduced gold. In what might be considered as young nuclei, the membrane is not furrowed or bui slightly so, and the chromatine is usually quite distmct, arranged in short, variously looped pieces along .!:- long axis of the nucleus, or in the form of minute nodules (nucleoli) m ditlcrent positions in the nuclear cavity (rig. a, 1 and 21). The reticulum of achromatine, or, better, caryoplasma, with the meaning attributed to that term by Carnoy, is very delicate with vcrv narrow meshes in the nuclei just referred to. A very large number of the nuclei observed lacked chromatine while their caryoplasma was more prominent and its meshes larger. In a few, a further modification of the reticulum, to be described below, was observed. In view of Nicolaides'i ^^ork on the division of nuclei in the frog's muscle, I made a careful search for like cases of division in Necturus, but the result was disappointing. Out of many hundred nuclei which I examined I found but one case of division, and that from the heart-muscle (fig. a, II). Flemming^ ol 'p.d indirect division of the muscle nuclei in larval but not in adult Amphibia. My failure to find in Necturus what was observed bv Nicolaide^ in the fro^; couM not have been due to the reagent, gold chloride, for I found negative results when a mixture of chromic and acetic acids, or of these and osmic acid, was employed. Nine out of ten of the old nuclei, i. e. those in which there remains no trace of chromatine, hav- markings and furrowings on their surface. Sometimes, as in fig. a, 2, a series of parallel > " Uebcr die Karjokinetisclie Ersclicinungen der Muskelkorpcr," ' Arcii. fiir Ana', uud Plijs., Piiys. Abth., 1S83, p. 441. 2 ' Zellsubstanz Kern- und Zelltlieilun-j,' Leipzig, 1882, p. 337. NOCLKl OK MUSCLE-FIDIiE IN NEUTURUS LATERALIS. 463 funows occupy one part of the surface of the merabrauc, the remaiuder of which is possessed of a series running in a contrary direction. They may be arranged parallel to the length of the fibre, or, as in 8, perpendicular to the long axis of the nucleus, or, as in 7 and 9, oblique to the same. Often one finds a combination of the two last mentioned modes of arrangement as represented in 10. Cases were observed lu which a furrow, followed a part of the way around the nucleus, was found to divide at an acute angle, the branches completing the rest of the nuclear circumference. If the nucleus is flattened it is usual for the furrows to be confined to one surface. In 7 and 9 the number of these is respectively three and two, and in 8 thev are verv numerous. The depths of the furrows vary with u'leir breadth, the latter being estimated by the breadth of the violet line of reduced gold. The depth in some nuclei is such that when one takes an optical section of them the nuclear cavity is almost divided into <^ series of separate compartments (25). The distance of the furrows from each other is subject also to considerable variation (10, 12, 15). The cause of these furrows is in all probability the pressure exercised by the trabeculfc of the muscular reticulum described bv Melland,' the transverse trabeculifi giving rise to the trans- verse furrows, the longitudinal ones to the furrows runmng parallel to the long axis of the nucleus. Here ia passing I mav refer to my own observations on this muscular reticulum. These were made on specimens obtained with gold chloride from the rabbit, frog, Necturus, crayfish, and grasshopper, and as a result I accept in full the views of Melland. In my preparations of the muscle-fibre obtumed from the rabbit and Necturus this reticulum is in all its aspects splendidly demonstrated. Carnoy^ apparently holds the same view as to the cause of the striation of the muscle-fibre in Hydrophilus piceus, for he describes it as due to a re- arrangement of the reticulum of the cell (cytoplasma of that i "A Simplified View of the Histology of the Striped Muscle-fibre," this Journal.July, 1885, p.371. ■' ' La Biologic CcUulaire,* Paris, 1884, pp. 102 aud 193, fig. 38. ^& 4Gi A. B. MACALLUM. author) in longitudinal and transverse trabecute, the myosine arising from that pirt of the cellular contents enclosed in the meshes of the primitive reticulum of the cell. It is not too great an inference to draw that this reticulum is the true contractile element, while the myosine shifts and accommodat ,-s itself to the cr-.ditions of the latter, ^r: .apport of this I refer to fig. a, 6 and 13, in which one sees that the furrowiDg takes the shape and arrangement of the meshes ot the reti'julura. , . • , Why the furrowing on the surface of some nuclei is longitu- dinal only, on others transverse, I cannot with certainty say. Of one thing I am sure : where one series of parallel furrows alone is visible, thes- are in by far the greater number of cases transverse to the Ion axis of the nucleus. The greater part of the muscle-fibre use in my preparations was in the uncon- tracted condition, and it is in this condition that the mus.les are for the greater part of life. Following out the theory as to muscular contraction, given in the last paragraph, it is to be supposed that during rest the transverse trabeculde of the muscle reticulum are contracted, but lengthened during contraction ot the fibre, the conditions with regard to the longitudinal trabe- culEe being in the reversed order. As now the contraction or shortening of the transverse trabeculte must occur during the greater part of the life of the muscle, or during its resting periods, it is obvious that transverse furrows should be seen on the nucleus ofteuer and more prominent than longitudinal onas or than both combined. In this way we may explain away part of the ditficulty of i jcounting for th*^ occurrence of one or other series only of furrows. E. Weberi found that the nuclei of the frog's muscle are provided vHh longitudinal striae, which he thought due to the pressure exercised by the muscular fibriliae. 1 endeavoured for the sake of comparing them with the nuclei in Necturus to isolate, after the manner already described, the nuclei of the frog's muscle, but I met with a ve-.y indiflferent success. In > " Note bur lea noyaux des muscles stries cLei la grcncuille adulte," ' Arcliives de Plijsiologie,' 1S74-, p. 489. x^UCLEl OF MUSCLE-FIBRE IN NECTUIIUS LATERALIS. 4G5 the case of the few isolated, however, I coukl make out a cer- tain amount of trausverse striation of the membrane. Further, as to the trausverse furrows beiug often at acute angles with one another, an explanation for this may be found in the facts now to be described. A few nuclei presented other appearances than those men- tioned (fig. A, 9, 15, 16, 18, 19). Here the form of a oblong- meshed reticulum like tliat of the muscle-fibre was observed and considered by me at first to be caused by an impression pro- duced by the latter on the surface of the nuclear membrane. I found, however, in cases where it could admit of no doubt, that the reticulum was not on, but within the nucleus. In other words, there is in the interior of some nuclei a reticulum like in every respect to that found in the muscle-substance. In these cases no chromatine or caryoplasma could be observed. On the other hand, I observed a few nuclei in which the caryoplasma was approximately square meshed (fig. a, 23). The quadrangular form of the m'ishes is exhibited oftener and better in the nuclei from the heart muscle (fig. a, 20, 21). This form of the reticulum appears to be one of the stages transitional between the reticulum of the young nucleus and that . ferred to in the last paragraph. In view of these facts it is safe to infer, as Carnoy and Melland have done, that the muscle reticulum is simply the modified cytoplasma, the caryoplasma being derived from the latter.i Nuclei with such a modified caryoplasma as represented in fig. A, 20 and 21, must be capable of movement, or contraction and extension. This movement has been observed in the nuclei of vegetable cells by Banstein,- and in the nuclei of white blood- corpuscles of Necturus by Gage,-^ and is amossboid in character. But the possession of a square-meshed reticulum implies exten- sion and contraction in definite directions — the nucleus con- ' See Caruoy, op. cit., p. 250. - • Bot. Zcit.,' 1872, p. 22. ' ' Science,' Jan. 8tb, 1886. 466 A. B. MAf!ALLUM. tracts with the muscle-fibre and extends with it again, yet not pasoively. The possession of an irregularly meshed reticulum by the nucleus' would imply on the part of the latter movements, if any at all, of an amoeboid character. It is possible that this is just what occurred in the nuclei represei.. jd in fig. a, 10, 12, and 17, an unequal extension or contractiou of all parts of the nucleus, resulting in a misplacement of the furrows and in their irregu- larity. Nicolaides suggests that all muscle nuclei take a more than passive share in muscular contraction. S jme nuclei have part of their surface completely free from furrows (fig. a, 5). I think this is due to the fact that the whole of the nuclear body is not surrounded by the muscle-substance, a part of it lying between the latter and the sarcolemma. ' EXPLANATION OF PLATE XXXIII, figs. A and B. Illustrating Mr. Macallum's Paper on the "Nuclei of the Muscle-fibre in Neeturus lateralis." Fig. A,l — 25. — Nuclei of striated muscle-fibre of Neeturus lateralis, 11, 20., 21, 22, representing some from the heart muscle. Mode of preparation : gold chloride, formic acid. Fig. b. — A part of a striated muscle-fibre with its nuclei, from Neeturus. Gold chloride, formic acid. (Note. — In drawing these figures, Leitz obj. 7, and oc. 1 or 3 wcic employed.) .