IMAGE EVALUATION TEST TARGET (MT-3) 1.0 I.I 1.25 ^ 1^ iiiii 2.2 20 1.8 1.4 1.6 Photographic Sciencea Corporation 4^ "% •sj f\ S^. ^ O 'C^ .^V -L^ k '^^ 23 WEST MAIN STREET WEBSTER, N.Y. 14580 (716) 872-4503 CIHM/ICMH Microfiche Series. CIHM/ICIVIH Collection de microfiches. Canadian Institute for Historical IVIicroreproductions / Institut Canadian de microreproductions historiques Technical and Bibliographic Notes/Notes techniques et bibliographiques The Institute has attempted to obtain the best original copy available for filming. Features of this copy which may be bibliographically unique, which may alter any of the images in the reproduction, or which may significantly change the usual method of filming, are checked below. a Coloured covers/ Couverturs de couleur I I Covers damaged/ D D D D n Couverture endommagie Covers restored and/or laminated/ Couverture restaur Ae et/ou peliiculie I I Cover title missing/ Le titre de couverture manque I I Coloured maps/ Cartes giographiques en couleur Coloured ink (i.e. other than blue or black)/ Encre de couleur (i.e. autre que bleue ou noire) I I Coloured plates and/or illustrations/ Planches et/ou illustrations en couleur Bound with other material/ Relii avec d'autres documents Tight binding may cause shadows or distortion along interior margin/ La re liure Sarrie peut causer de I'ombre ou de la distorsion le long de la marge int6rieure Blank leaves added during restoration may appear within the text. Whenever possible, these have been omitted from filming/ II se peut que certaines pages blanches ajouties lors d'une restauration apparaissent dans le texte. mais, lorsque cela Atait possible, ces pages n'ont pas ixi filmies. L'Institut a microfilm^ le meilleur exemplaire qu'il lui a 6X6 possible de se procurer. Les details de cet exemplaire qui sont peut-dtre uniques du point de vue bibliographique, qu< peuvent modifier une image reproduite, ou qui peuvent exiger una modification dans la mithode normale de filmage sont indiqu6s ci-dessous. □ Coloured pages/ Pages de couleur n D Pages damaged/ Pages endommagies Pages restored and/or laminated/ Pages restaurdes et/ou pelliculdes Pages discoloured, stained or foxed/ Pages d^colories, tacheties ou piqu^es Pages detached/ Pages d6tach6es rTj Showthrough/ Transparence Quality of prir Quality inigale de I'impression Includes supplementary materii Comprend du matiriel supplimentaire Only edition available/ Seule Edition disponible I I Quality of print varies/ r~l Includes supplementary material/ r~~l Only edition available/ D Pages wholly or partially obscured by errata slips, tissues, etc., have been refilmed to ensure the best possible image/ Les pages totalement ou partlellement obscurcies par un feuillet d'errata, une pelure, etc., ont 6ti filmies d nouveau de fapon d obtenir la meilleure image possible. Additional comments:/ Commentaires supplimentaires; Pagination as follows : [303] -307 p. This item Is filmed at the reduction ratio checked below/ Ce document est filmi au taux de reduction indiquA ci-dessous. 10X 14X 18X 22X 26X SOX i 7 12X 16X 20X 24X 28X 32X Th0 copy filmed h«r« has b—n raproducad thanks to tha ganarosity of: Medical Library McGill University ■Montreal Tha imagas appearing hara ara tha bast quality possibia considaring tha condition and lagibiiity of tha original copy and in icaaping with tha filming contract spacificationa. L'axamplaira film* fut raproduit grflca A la ginArositi da: Medical Library McGill University Montreal Laa imagaa suivantaa ont 4t* raproduitas avac la plua grand soin, compta tanu da la condition at da la nattat* da I'axampiaira film*, at an conformity avac laa conditiona du contrat da filmaga. Original copies in printed paper covers are filmed beginning with the front cover and ending on the laat page with a printed or illustrated imprea- sion, or the back cover when appropri.ita. All other original copies are filmed beginning on the first psge with a printed or illustrated impree- sion, and ending on the laat page with a printed or lliuatratad impression. Les exempleires originaux dont la couverture en papier eat imprimie sont filmte en commenpant par la premier plat at en terminant soit par la darnlAre page qui comporta une empreinte d'Impression ou d'iliustration, soit par la second plat, salon la cas. Tous laa autres axemplairaa originaux sont filmte an commandant par la pramiAre page qui comporta une empreinte d'Impression ou d'iliustration at en terminant par la darniAre page qui comporta una telle empreinte. The laat recorded frame on each microfiche shall contain the symbol —»•( meaning "CON- TINUED"), or the symbol V (meaning "END "). whichever appiiaa. Un das symbolas suivants apparattra sur la darnlAre image de chaque microfiche, seion le cas: le symbols — »> signifie "A SUIVRE", le symbols ▼ signifie "FIN". Mapa. plates, charts, etc., may be filmed at different reduction ratios. Those too large to be entirely included in one exposure are filmed beginning in the upper left hand corner, left to right and top to bottom, aa many frames aa required. The following diagrama illustrate the method: Lee cartea. planches, tableaux, etc., peuvent itre filmia A daa taux da reduction diffirents. Lorsque le document est trop grand pour Atra reproduit en un seul clichA. il est film* A partir de Tangle supArieur gauche, de gauche h droite. et de haut en bas, an prenant le nombre d'images nicessalre. Les diagrammes suivants illustrant le m6thode. 1 2 3 I 1 2 3 i 4 5 6 THE MUSCULUS STERNALIS AND ITS NERVE- SUPPLY. By Francis J. Shepherd, M.D., Professor of Anatomy in M'Gill University, Montreal. The subject of the musculus stemalis and its nervp-supply has been so exhaustively treated by Professor Cunningham of Dublin in a recent number of the Journal^ that it would appear superfluous for me to ada anything further, had not Professor Bardeleben^ of Jena still more recently recorded twelve additional cases of the musculus sternalis observed by him since 1876. In this paper he states that, in every case in which the nerve-supply was traced, it came from the intercostals (generally from the 3rd and 4th), and he seems to doubt the possibility of the true " stemalis " muscle receiving its innervation from the anterior thoracic. Thus it appears that there is still a considerable difference of opinion regarding the nerve-supply of this very puzzling muscle, and for this reason I wish to place on record three additional cases in which the nerve-supply was traced. Professor Bardeleben makes no refer- ence in his paper to the observations of Professor Cunningham and others on this subject. It seems strange that the observa- tions of anatomists, other than German, should have been overlooked or disregarded, especially as the number of cases reported by Dr Cunningham, where the nerve-supply was traced to the anterior thoracic nerves, far exceeded in number those recorded by Professor Bardeleben. In vol. xix. of this Journal'^ I published a paper on the occurrence of the musculus stemalis in anencephalous monsters, and stated that I had found nine muscles in six foetuses ; in six the nerve-supply was traced to the anterior thoracic, in one to the anterior thoracic and intercostal, and in two it could not be made out. Since the publication of that paper I have examined three anencephalous foetuses and one cyclopean. In one anen- ^ Vol. xxii. p. 392. - AiMtomisclier Anzeigcr, May 1888, IToa. 11 and 12. " P. 311. 304 PROFESSOR FRANCIS J. SHEPHERD. cephalous foetus, a male, no stemalis muscle was found, nor was any found in the cyclopean ; but in the other two, both females, three well-developed " stemalis " muscles existed. This makes a total of twelve ".Htemalis" muscles observed in nine anen- cephalous foetuses, and in ten of these muscles the nerve-supply was traced. Case VII.' — Female foettis, anencephalous, with spina bifida in cervical region. Musculua stemalis bilateral. Great pectoral of each side deficient. Nerve-supply from internal anterior thoraxiic. On both sides the muscle is of large size. The right muscle is continuous above with the sterno-mastoid, and arises from the first piece of the sternum in common with the great pectoral. It passes downwards and outwards, expanding into a large, flat muscle which is inserted into the 5th, 6th, and 7th ribs immediately external to their cartilages. The most external fibres of the muscle are blended with the lower portion of the great pectoral, while the innermost fibres continue down over the pectoral muscle to end in the aponeurosis of the external oblique muscle. The central portion of the great pectoral which arises from the costal cartilages of the 2nd, 3rd, and 4th ribs is absent, so that a triangular interspace of con- siderable size is left between the existent upper and lower portions of the pectoralis major ; in this interspace a nerve is readily found which reaches the " stemalis " about its middle, and supplies it by piercing its under surface. On tracing back this nerve it is seen to be branchless until it reache the upper border of the lesser pectoral, where it joins the internal anterior thoracic, and gives a branch of considerable size to the lower portion of the great pectoral. None of the intercostal nerves can be traced to the " stemalis ; " they are seen to loop around the inner border of the muscle, but do not pierce or supply it. The left muscle is also of large size, but more fusiform in shape and more oblique in direction. It is attached above to the second piece of the sternum ; having an origin in common with the great pectoral, it passes downwards and outwards over the lower portion of that muscle and ends in the aponeurosis of the external abdominal oblique. A much larger portion of the 1 These cases are numbered consecutively with those recorded in vol. xix. THE MUSCULUS STERNALIS. 806 great pectoral is deficient than on the opposite side, and in this interspace is seen a long branchless nerve coursing towards the " stemalis " muscle and supplying it from its outer surface. This nerve has exactly the same course and distribution as its fellow of the opposite side, and is a branch of the internal anterior thoracic. The intercostals recur around the inner border of the muscle, but do not pierce or supply it. In those cases where the great pectoral is deficient I can now, with the greatest ease, find the nerve supplying the stemalis ; it is always in the same situation, in the interspace between the upper and lower portions of the great pectoral. Case VIII, — Anencephaloua Female Foetus; spina bifida in the cervical region. Hare-lip. Musculus stemalis unilateral. No deficiency in the great pectoral. Nerve-supply frorfi both the internal anterior thoracic and the intercostal (see fig. 1). "C. Fig. 1. — Single stemalis of left side, h., inner cord of brachial plexus ; c, 3rd in- tercostal nerve sending branch to muscle ; s. , branch of internal anterior thoracic piercing pectoral muscle, and also going to stemalis; e.a.t. and i.a.t., external and internal anterior thoracic nerves ; g., upper part of great pectoral muscle ; p.m., pectoralis minor. On the left side is a well-marked " stemalis " muscle. The muscle is ribbon-shaped and of no great size, but quite distinct. Above it is attached to the lower part of the first piece of the sternum by a fibrous origin; it soon becomes muscular, and 306, PROFESSOR FRANCIS J. SHEPHERD. continues in a downward and oiitward direction over the great pectoral and a little outside the sternum, to become lost in the abdominal aponeurosis. The muscle is in no way connected with the great pectoral. A small, slender nerve is seen piercing the great pectoral about its middle, and on a level with the upper border of the third rib ; it passes upwards and inwards to the upper part of the sternalis, which it supplies from the under surface. When traced back, this nerve is seen to come from the internal anterior thoracic ; before it pierces the pectoralis margin it gives off several branches to that muscle. The internal an- terior thoracic, when dissected out, has the following course : — After being given off from the inner cord it passes inwards, and is joined by a branch from the external ; before piercing the costo- coracoid membrane it gives off a large branch to the lesser pec- toral ; it then passes over the lesser pectoral, giving branches to lower part of the great pectoral, as it proceeds inwards between the great and lesser pectorals? ; before piercing the great pectoral, and while in the substance of that muscle, it gives off numerous branches of supply, and then proceeds inwards to supply the " sternalis." On examining the intercostal ner'es, the third is seen to pass under the " sternalis," and to hook abound the inner edge ; as it does so it gives off a large branch of supply to the lower part of the " sternalis." None of the other intercostals are distributed to the sternalis. As I mentioned above, I have now traced the nerve-supply to ten of these muscles, occurring in anencephalous foetuses, with the following result: — All were supplied by the anterior thoracic ; two muscles also received an additional supply from the intercostals. Now, in every case where the great pectoral was deficient, the nerve supply was derived from the anterior thoracic nerves alone ; and in the only two cases in which the " sternalis " occurred without deficiency of the great pectoral the muscle had a double nerve supply, viz., from the anterior thoracic and intercostals. This almost seems to indicate that there are two different kinds of " sternalis " muscles. Barde- leben^ holds that, excluding those cases of so-called " sternalis" which belong to the platysma or pectoral varieties, we have left the "typical sternalis," which usually extends from the rectus sheath * Loc. cit. THE MUSCULUS STERNALIS. 307 to the sterno-mastoid, and belongs to the muscuhir system of the rectus abdominis and pubo-hyoideus, and derives its nen'e-supply from the intercostals. He suggests that it should be called the " rectus abdominis superjicialis." In my cases the muscles supplied by the intercostals also received a special nerve-supply from the anterior thoracic. This would seem to point to a form of sternalis intermediate between those supplied on the one hand altogether by the anterior thoracic, and on the other by the intercostals.^ I do not think that any one who has seen in the anencephalous foetus a well-marked specimen of the " sternalis " muscle, accom- panied by deficiency of the great pectoral, could fo.* a moment doubt that it was the missing portion of the pectoral, which had become displaced or rotated, even if he were ignorant of its nerve-supply. In those cases, however, where there is no defi- ciency of the great pectoral, and where the sternalis muscle is quite superficial and unconnected in any way with the great pectoral, the case is not so clear, especially if the nerve-supply be partly or wholly (as in the cases reported by Professor Bar- deleben) derived from the intercostals. I confess that in these cases my ideas as to the homology of the sternalis are not at all settled. Perhaps a wider knowledge of the myology of the various animals will in the future throw some fresh light on the subject. The occurrence of this muscle so commonly in anencephalous monsters would rather point to its being a rever- sion, and not a new muscle appearing in man. ^ I have, however, never yet been fortunate enough to meet with a " sternalis " mv-scle altogether supplied by the intercostals, and I imagine, if the branch from the anterior thoracic were looked for carefully, it would always be found.