176 



" In shape the heart was very elegant ; it was compressed, and both 

 ventricles described the half of a circle, and ended in a short sharp 

 apex. The length and breadth of this organ were equal, the admea- 

 surements being each 1-| inch. 



" The disposition of the branches given off at the arch of the aorta 

 Vas as follows. On the right side arose a common trunk, which di- 

 vided into the right subclavian and the right carotid, but gave off 

 lower down to the left the left carotid. The left subclavian arose 

 from the aorta in a distinct branch. 



" In his account of the anatomy of Capromys Mr. Owen notices 

 a peculiarity in the arrangement of some of the abdominal mus- 

 cles : a decussation of the pillars of the recti muscles taking place 

 at the pubes. In the Coypus an arrangement of a similar cha- 

 racter was observed. It may be thus described. From the right 

 OS pubis and close to the symphysis arises a fleshy column, which 

 crossing a column arising from the left side passes obliquely up- 

 wards, and becomes immediately united with another larger column 

 arising more outwardly, and passing under the column of fibres from 

 the left side, as the first does above it ; and thus is constituted the 

 left rectus muscle. Between these two columns, as we have said, 

 and from the left side of the pubes, runs up a decussating column, 

 which blends with another passing beneath the larger column of the 

 left rectus, both forming by their union the right rectus abdominis. 

 The lower column of the external oblique, with which muscle the 

 rectus is blended above (as in Capromys) so as to appear in reality 

 but one, has its own insertion on its own side. 



"The testes were situated in the groin on each side of the. pubes, 

 enveloped in a strong cremaster of circular fibres given off from the 

 external oblique and transversalis ; they were capable of being pass- 

 ed back through the abdominal ring, which is very large, the columns 

 of the rectus forming its inner edge. As in many others of the Ro- 

 dent order, large foliated fatty processes, adhering to the testes, were 

 found hanging loose in the abdominal cavity ; their length was 5 

 inches, their breadth at the broadest part 2. 



" The bladder was of the usual oval form, and, as it lay undistend- 

 ed with fluid, measured 2 inches in length. The ureters entered la- 

 terally near its neck. 



" Beneath the ureters near their entrance the vasa defer entia 

 crossed : the total length of these tubes was 5 inches ; at their origin 

 on leaving the epididymis they were found to be slightly tortuous, 

 but only for a short distance. The epididymis consisted of a congeries 

 of convolutions, whence a tortuous elongated portion followed the 

 convex surface of the testis for two thirds of its length, and then 

 passed into the vas deferens, which was enveloped in a fatty process 

 extending from the testes, and spreading over the base of the vesi- 

 culce seminales and the proximate portion of the ureters. The vesiculce 

 seminales were long tortuous bodies with numerous small processes 

 or sacculi, giving them a knotted appearance : at their apex they 

 folded down upon themselves, and terminated in a point : when ex- 

 tended they measured about 4 inches. 



" The urethra at its commencement formed a sort of cul de sac. 



