719 



terior thoracic, since that nerve and the lateral thoracic are exceedingly 

 variable in their mutual relationships, size and area of supplj^ 



It has been suggested that the sternalis may be a remains of 

 the panniculus, a downward extension of the platysma, or as was sug- 

 gested by DOBSON ^) a representative of the sterno-cuticularis or 

 sterno-facialis of the hedgehog. On this point it may be noted that 

 the sternaHs always lies on a totally different plane from the platysma, 

 and one which is much deeper comparatively speaking. I saw on- 

 ce in a hydrocephalous foetus the platysma descending in well-marked 

 bands as low the level of the nipple. It was superficial to the fascia 

 covering the pectoralis major and could not possibly have been mista- 

 ken for a sternaHs muscle on account of its position. Shepherd in his 

 first paper on the subject has a similar observation on an anencephalous 

 foetus. „In one case" he says „the right platysma myoides was well 

 developed, and passed some distance below the clavicle. It was se- 

 parated from the musculus sternalis of that side by fascia and a thick 

 layer of fat, and was on a plane quite superficial to the musculus 

 sternalis.'" Teichmann has also seen the platysma descend as low as 

 the third rib. 



The theory which regards the sternalis as an extension upwards 

 of the rectus abdominis, appears to me to be altogether negatived by 

 the fact that in all cases, so far as my dissections of a large number 

 of animals have shown me (the chrysochloridae are according to Dob- 

 son an exception to this rule) when the rectus ascends higher than in 

 Man it does so beneath the pectoralis and therefore on too deep a 

 plane to be associated with the sternalis. It may possibly be that 

 such a rotation of the abdominal part of the pectoral mass as I have 

 described above, may have been taken for an upward extension of 

 the rectus. 



Birmingham, October 21, 1889. 



1) Journal of Anatomy and Physiology, vol. XVII, p. 84. 



