UPPER HALF OF RABBIT. 19 



muscular bellies of the pronator and the flexor muscles arising from the ulna 

 and internal condyle of the humerus have Been cut through and reflected to 

 show this insertion of the biceps. 



This dissection contrasts with a similar dissection of the human subject 

 in the imperfection of the clavicles ; in the absence or rudimentary con- 

 dition of the omo-hyoid', in the presence in the neck of two additional 

 muscles, the acromio-basilar, n, and the cleido-occipital, m ; in the formation 

 of a compound * cephalo-humeral ' muscle, as in many other mammalia, by 

 the physiological combination of the cleido-mastoid, k, the cleido-occipital r , 

 m, and the acromio-basilar, n, with the deltoid, f\ in the prolongation of 

 the sterno-clavicidar, g, and ster no -scapular muscles, h and i, the homo- 

 logues of the subclavius, on to the spine of the scapula at /, whence they 

 act in the way of slinging up the horizontally-carried trunk ; and, finally, in 

 the greater size of the cervical platysma, x, and the development of a cuta- 

 neous muscle, 8, the ' dermohumdrien* s, ' costoalaris] s, ' brachiolateraV, in 

 the regions of the back and flanks. The cleido-occipital, k, the acromio- 

 basilar , n, and the ' latissimo-condyloideus', e, are more or less frequently 

 represented by muscular varieties occurring in the human subject, and the 

 absence of any scalenus anticus in the Rabbit is paralleled in man by the 

 occasional perforation of the fibres of that muscle by the upper factors of 

 the brachial plexus, one of which, the fifth cervical, has been observed to 

 pass entirely in front of the muscle. The digastric, M, the biceps, /, and the 

 pectoralis minor, e, present points of difference, stated above, in which the 

 Leporidae and very many other mammals coincide with each other and 

 differ from man. The rectus abdominis is very usually prolonged in mam- 

 malia lower than man up to the second or first rib, and in the rabbit up 

 even to the base of the manubrium ; when thus prolonged, it is known as 

 the ' rectus thoracis! It is frequently crossed at its upper end, as here, by 

 a muscle known as the ' sterno-costalis', passing downwards and covering 

 the front of the rectus just as the external oblique does that of the rectus 

 abdominis. It may be better however to speak of the sterno-costalis as 

 being a lateral efflorescence of the rectus \ 



On the other hand, the arrangement and relations of the various struc- 

 tures of the lowly organised mammal here figured are sufficiently similar to 

 those of man to cast considerable light upon some even of the more intri- 

 cate points of anthropotomy. Among them we may specify the occurrence 

 of certain varieties in muscles, the relations of the deep cervical fascia, /3, 

 and the insertions of the pectoral muscle, c and d. 



1 For a discussion of the homologies of the rectus thoracis and the sterno-costalis, see Professor 

 Turner, Journal of Anat. and Physiol. May, 1867, pp. 247-253; May, 1868, pp. 392-394; Wood, 

 Ph. Tr. for 1870, pp. 110-112, vol. 160. These two muscles are not lettered in this figure, but 

 are seen to form a triangle with part of the first rib for its base and with its apex covered by the 

 sterno-clavicular muscle g. For a figure showing the rectus abdominis giving off a part of the 

 pectoral, see Ecker, Anatomic des Frosches, 1864, p. 95. 



C 2 



