38 PROCEEDINGS OF THE ACADEMY OF [1889. 



THE STERNALIS MUSCLE. 

 BY S. W. WILLISTOST, M. D. 



Of the many interesting muscular anomalies of the human subject, 

 few, if any, have been more enigmatical than the sternalis. At 

 various times, and by various observers, since the days of Albinus, 

 and earlier, it has been regarded as a continuation of the rectus 

 abdominis, perhaps the most prevalent view, and endorsed by Bar- 

 deleben ; as a part of the stern o-mastoid ; as pertaining to the panicu- 

 lus carnosus group, a view which the eminent anatomist Turner has 

 favored ; as a muscle sui generis, without homologue in other 

 animals ; or as a muscle of the pectoral group, which seems to be the 

 most probable, as well as most recent theory. Neither can we say 

 whether the muscle is vestigial or rudimentary — I use the words in 

 Ryder's sense — though evidence points to the former. But if a 

 vestige, and not a muscle developing, we ought to find a counter- 

 part of it in other animals, which, so far, has not been done, unless 

 indeed, we call it a skin-muscle, which seems very improbable. 

 What then is it, and what are its functions ? 



From Gruber's 1 and Turner's 2 researches, it appears to occur in 

 the normal human subject, in some form or other, in about three 

 per cent, of all cases. In its normal or typical form, as represented 

 in the case figured herewith, it appears to occur in less than one per 

 cent, of all cases. But, while so abnormal in the normal subject, 

 it appears to be normal in the abnormal subject,- — that is, it is 

 almost invariably present in anencephalous monsters. Abraham 3 

 found it in six out of seven anencephali, Shepherd 4 in eight out of 

 nine. The latter adds " the fact that this muscle occurs so 

 commonly in the brainless monsters would point rather to its being 

 a rudiment than a new muscle appearing in man." Anencephali 

 are usually females ; perhaps that fact may add strength to Albrecht's 

 argument that woman approaches the brutes in structure more 

 than does man ! 



However, as first suggested by Abraham, affirmed by Cunningham 5 

 and confirmed by Shepherd, it seems probable that the muscle belongs 



1 Mem. de l'Acad. Imp. de St. Petersbourg, iii, I860. 



2 Journ. Anat. and Phys. 1. 246, 1867. 



3 Trans. Acad. Med. in Ireland, i, 1883. 



4 Jour. Anat. and^Phys. xix, 1885; ibid, xxiii, 18S9. 

 6 Journal Anat. and Phys. xviii, 1884. 



