BY W. J. McKAY. 949 



Pretrahentes costarum superiores. 



Mm. 'pretrahentes costarum, Owen; Inter costales superiores, Hoff- 

 mann ; Obere, lange Ztoischenrippenmiiskeln, D'Alton ; Stratum 

 quintiim, Hiibner ; Vorderer, gezahnter Mushel, Meckel ; Great 

 lateral costal muscles, R. Jones. 



The pretrahentes superiores arise from the junction of the inner 

 with the middle third of the superior border of the riVj, close to the 

 point of insertion of the levatores costarum group. Each muscle 

 runs outwards, backwards, and downwards, to be inserted into the 

 ninth rib from the origin at the junction of the middle with the 

 outer third. Each muscle as it passes back gives slips of insertion 

 to all the ribs that it passes over. The muscle arises by long 

 thin tendons which are closely connected with the tendons of inser- 

 tion of the sacro-lumbalis. 



Each bundle of an anterior portion of the muscle is external to a 

 posterior bundle. The muscles, taken as a mass, form well-marked 

 prominences on the sides of the snake, and help in a greater measure 

 to determine the bulk of the snake. Home and E. Jones describe 

 each bundle of these muscles as running over four ribs only ; this, 

 however, is not correct. As stated above, we believe these muscles 

 to be modified external intercostals. The large lateral branch of 

 the intercostal nerve that leaves the anterior of the body, is chiefly 

 distributed to this muscle, and the next to be described. 



Pretrahentes costarum inferigres. 



Mill, intercostales inferiores, Hoffmann ; Untere lange Zwisclienrip- 

 penmuskeln, D'Alton ; Stratum sextum, Hiibner ; Aeusserer schiefer 

 Bauchinuskel, Meckel ; Extension of the pretrahentes superiores^ 

 Owen ; Great inferior costals, R. Jones. 



The pretrahentes inferiores arise from the ribs at the point 

 where the superiores are inserted, and running back nearly parallel 

 with the long axis of the body, they are inserted on the ninth rib 

 from the origin. As they run back they likewise give slips to the 

 ribs over which they pass. The muscles are sometimes described 



