THE LIVER 



l8 3 



and cephalic end of the colon to descend toward the pelvis (Fig. 174). The 

 ascending colon is thus formed and the vermiform appendix takes the position 

 which it occupies in the adult. The development of the mucous membrane 

 of the intestinal tube has been described by Johnson (American Journal of 

 Anatomy, vols, io, 14 and 16, pp. 521-561; 187-233; 1-49). 



Ascending 

 mesocolon 



Ascending 

 colon 



Ccecum 



Ascending 

 colon 



Ccecum 



Processus 

 vermiformis 



Processus 

 vermiformis 



Fig. 175. — The caecum of a human embryo of 5 cm. (Kollmann). A, from the ventral side; B, from the 



dorsal side. 



THE LIVER 



In embryos of 2.5 mm. the liver anlage is present as a median ventral out- 

 growth from the entoderm of the fore-gut just cranial to the yolk-stalk (Fig. 

 161 B). Its thick walls enclose a cavity which is continuous with that of the gut. 

 The liver anlage is embedded in the ventral mesentery which lies in the median 

 line between the fore-gut, the ventral body wall, and the septum transversum 

 (Fig. 1 7 1 A) . Thus, from the first the liver is in close relation to the septum trans- 

 versum and later when the septum becomes a part of the diaphragm the liver 

 remains attached to it. 



In embryos 4 to 5 mm. long, solid cords of cells proliferate from the ventral 

 and cranial portion of the liver anlage. These cords anastomose and form a 

 crescentic mass with wings extending lateral and dorsal to the gut (Fig. 171 A). 



