ELISHA MITCHELL SCIENTIFIC SOCIETY. 15 



Opposite side; and is inserted on the first, second and 

 third ribs, the chief insertion being- on the first. 



At about the level of the ensiform cartilage, the mus- 

 cle g-ives off a small slip, which is inserted along- with 

 its fellow of the opposite side, into the aponeuroses of 

 the external obliques, in the median line, beneath the 

 posterior (fifth) -pectorals. 



The rectus abdominis is ensheathed in the aponeu- 

 roses of the two obliques and the transversalis. Pos- 

 teriorly all these aponeuroses lie ventral to it. Ante- 

 riorly the aponeurosis of the external oblique is ven- 

 tral, but the aponeuroses of the internal oblique and 

 transversalis are dorsal to it. 



Synonom3\ Droit-abdominal, S.-D., vol. II, p. 307; 

 rectus abdominis, M., p. 142; rectus abdominis, G. & 

 T., p. 29. 



The slip g"iven off in region of ensiform cartilag-e, is 

 not mentioned by the writers cited above. It probably 

 corresponds to the fibres said to be attached to the en- 

 siform cartila^Jfe in human anatomy."^ 



* Quain's Anatomy, 10 ed., vol. II, pt. 2, p, 334. 



Our account of the rectus sheath differs from that 

 of Strauss-Durckheim, in that we do not find the apon- 

 eurosis of the internal oblique dividing- into ventral and 

 dorsal limbs which embrace the rectus anteriorly, as 

 already mentioned in connection with the internal 

 oblique. Mivart, and Gorham and Tower, overlook 

 the insertion of the posterior part of the transversalis, 

 and thus g-ive an imperfect account of the sheath. 



PECTORAL MUSCLES. 

 The pectoral muscles form a triang-ular mass on the 

 front of the chest, running- from the median line of the 

 body to the arm. The mass is divisible into ^\^ dis- 



