DIGESTIVE TRACT OF THE CAT. 



23 



winds about it, and this pressure tends to push the colon 

 and caecum as far to the left side of the body as is possible. 

 It seems to me that this pressure, together with a dispropor- 

 tionate growth of the colon, presents a probable explanation 

 for the strange position of the caecum to the left of the 

 median line of the body. The migration of the caecum to 

 the left does not seem likely to be a curious coincidence or 

 an anomally, for this relation has been repeatedly observed, 

 each case differing only in degree. 



Fig. 13 represents the opened abdominal cavity of an 

 embryo 7 0 mm. The dissection is exactly the same as the 

 last one, but the embryo is not only larger, but is also more 

 advanced in development. We now find that the colon has 

 materially increased in length. At this stage the stomach, 

 spleen, great omentum, and kidney prevent its further growth 

 to the left. The stomach and liver interfere with its ex- 

 tension cephalad, the coils of jejunum and ileum as well as 

 the liver lie ventrad from it, and the fixed point of junction 

 of the duodenum and jejunum prevent its bodily movement 

 to the right. The caecum has no choice but to grow in a 

 transverse direction, and thus the colon is elongated and 

 the so-called tranverse colon is formed. 



Fig. 14 represents the opened abdominal cavity of an 

 embryo 73 mm. The dissection is the same as of the last 

 two embryos, except that the great omentum has been 

 opened in such a manner as to show the extremity of the 

 Spigelian lobe of the liver, and its relation to the stomach. 

 This organ is very obliquely placed, and so reminds one more 

 of the adult than of the embryo. 



Parts of the liver, spleen, and omentum have been re- 

 moved, as well as the greater portion of the jejunum and 

 ileum. The remaining organs present no difficulty in their 

 identification. This embryo differs materially in one respect 

 from the others, in that it possesses an ascending colon. 



The caecum continued its tranverse growth to the right 

 until it encountered certain obstacles, which forced it to 

 change this direction of growth. It met the duodenum. 



