174 



THE ENTODERMAL CANAL AND THE BODY CAVITIES 



colon, then bending abruptly caudad as the descending colon, returns by its iliac 

 flexure to the median plane and forms the rectum. 



A B C 



Fig. 181. — Three successive stages shomng the development of the digestive tube and the mesen- 

 teries in the human fetus (Tourneux in Heisler) : /, Stomach; 2, duodenum; 3, small intestine; 4, colon; 

 5, yolk stalk; 6, caecum; 7, great omentum; 8, mesoduodenum; Q, mesentery; 10, mesocolon. The arrow 

 points to the orifice of the omental bursa. The ventral mesentery is not shown. 



The caecum (Fig. 182) may be distinguished from the vermiform process at 

 65 mm. (C R) (Tarenetzky). The caecum and vermiform process make a U- 



Ascending 

 mesocolon 



Ascending 

 colon 



CcBCiim,' 



Ascending colon 



Processus, 

 vermiformis 



Cacum 



Processus 

 vermiformis 



Fig. 182. — The caecum of a human fetus of 50 mm. (Kollmann): A, from the ventral side; B, from the 



dorsal side. 



shaped bend with the colon at 42 mm. (C R), and this flexure gives rise to the colic 

 valve (Toldt) . In stages between 100 and 200 mm. (C R) the lengthening of the 



