394 MR. ST. fiEOBGL MIYART AND DR. J. MURIE [Jtllie 26, 



Serratus posticus. This is one single sheet, of muscle and fascia, 

 answering in all respects to the description given of that in Hyrax*, 

 with the exception that it reaches only to the fifth rib. Its fibres, 

 moreover, have a uniformly oblique direction, and take origin from 

 the ligamentum nuchse by a strong tendon. 



Meckel f avers that in some Rodents, principally the Agouti, Mar- 

 mot, and Beaver, it goes to all the ribs except the first. It was not 

 so in our specimen, and the alteration in the direction of the fibres 

 was not so clearly shown as Meckel has described. 



"We have found it in the Hare and Rabbit very thin and delicate, 

 almost like a fascia, except at the anterior part, where there are a 

 few muscular fibres. It appears to go to most of the ribs in the 

 Hare, indeed to all except the three anterior ones. In the very fleshy 

 old male Guinea-pig examined by us it was distinct and strong from 

 the third to the eighth or ninth rib. 



The sacro-himbalis has its usual attachments, and, emerging from 

 the mass of the erector spinpe, is prolonged, as the cervicalis ascen- 

 dens, to the transverse process of the sixth cervical vertebra. In the 

 other three Rodents it did not seem to reach further than the seventh 

 cervical. 



The longissimus dorsi is very much larger and more fleshy than 

 the preceding, but also has the ordinary attachments. It is pro- 

 longed into the neck as a transversalis cervicis as far as the atlas, 

 strong tendons going to all the cervical vertebrae. It is the same in 

 the Guinea-pig. In the Hare, only as far as the axis ? But in the 

 Rabbit it is, as Professor Huxley % has observed, very powerful and 

 attached to the large metapophysial processes. 



The external oblique is a most extensive sheet of muscle, and 

 almost of a uniform thickness from the median line of the abdomen 

 nearly to the back. It springs by digitations as far forwards as the 

 fourth rib, and its fibres blend with the rectus over the cartilages of 

 from the fifth to the tenth ribs. Posteriorly it is fixed to the an- 

 terior spine of the ilium ; and its insertion is by muscular and tendi- 

 nous fibres into the brim of the pelvis from the ilio- pectineal promi- 

 nence to the symphysis. It is in close connexion with the insertion 

 of the rectus, which it covers ; but the main part of its inguinal 

 fibrous insertion proceeds down the median line of the symphysis to 

 about its middle, and rather nearer to the posterior than to the ante- 

 rior end of the origin of the very broad gracilis (figs. 4 & 5, E. o.). 



The two most peculiar points of interest in this muscle are, 1st, 

 its attachment and close adherence to the rectus ; and 2nd, its having 

 the aponeurotic semilunar fascia stretching from the anterior spine 

 of the ilium to the ilio-pectineal eminence and symphysis so strongly 

 tendinous as to form well-developed Poupart's and Gimbernat's 

 ligaments. 



It is altogether a thin muscle in the Hare ; and neither in it, the 

 Guinea-pig, nor Rabbit, notably differs from that of the Agouti in its 

 attachments. 



* P. Z. S. 1865, p. 335. t hoc. cit. p. 107. 



\ Hunterian Lectures, Koyal College of Surgeons, 1805. 





