DIGESTIVE TRACT OF THE CAT. 



The two following sections show conclusively that in 

 the cat the enormous size of the liver forms the chief factor 

 in forcing the intestines to develop (during a certain period), 

 outside of the abdominal cavity proper, within the cavity of 

 the umbilical cord. 



Fig. 2 is a sagittal section of a cat embryo 15i mm. 

 The plate shows well the continuity between the coelom 

 proper, and the cavity of the umbilical cord. The enormous 

 size of the liver is most striking, as well as the size of the 

 mesenteric vessels. At this stage the superior mesenteric 

 artery is nearly two thirds the size of the intestine, so that 

 it, together with the portal vein, occupies a very appreciable 

 amount of space in the abdomen. The liver grows with 

 great rapidity, and to such an enormous size that it practi- 

 cally fills the abdominal cavity, so that those portions of the 

 intestine which develop at a somewhat later date have no 

 choice, but are forced to grow in the continuation of the 

 coelom, or, in other words, in the cavity of the umbilical cord. 

 The surface of the liver which lies in apposition with the 

 intestines is deeply grooved, which shows the pressure its 

 growth must exert upon them. Moreover, the liver itself 

 often oversteps the boundary line between coelom projDer 

 and the cavity of the cord, and a small bit of it, in this sec- 

 tion, may be said to be actually contained within the latter 

 cavity. In this embryo this is seen to a very slight degree, 

 but it is not very uncommon to find quite a large expansion 

 of the liver within this cavity, partially surrounding the in- 

 testinal coils. We have so frequently observed this phe- 

 nomenon that at one time the question became a pertinent 

 one as to whether it might not be the normal condition, and 

 if for a brief space of time the liver ought not to be consid- 

 ered as a constant occupant of this cavity. This would seem, 

 however, to be going too far; but to state that the liver is 

 often found there is certainly no exaggeration. 



A tra,nsverse section of this same stage of development 

 is also instructive. Fig. 3 represents a transverse section of 

 a cat embryo 15| mm. The section passes through the 



