THE INTESTINAL CANAL. 



1031 



peritoneal covering is not complete, but is reflected just below its upper end, 

 leaving the upper part of its posterior surface uncovered and connected to the 

 iliac fascia by areolar tissue. Berry has seen the same thing in 6 per cent, of 

 cases. The reflected peritoneum never makes a true mesocaecum. It may have 

 sufficient motility or length to enter a right inguinal or femoral hernia, and in 

 rare cases a left 'one. According to Treves, any'human caecum can be classified 

 under one of four types (Fig. 652). In certain monkeys we see a primitive form 



FIG. Gol.A, B, C, D, four types of human cseca. (Treves. ) 



where the crecum is short, conical, and broad at the base, with its apex turned 

 up and in toward the ileo-colic junction (Fig. 651, A). This type is seen early 

 in the human foetus. Next it grows in length more than in breadth, and this 

 type is seen in the human fcetus in Fig. 651, B. As development goes on the 

 lower part of the tube ceases to grow and the upper part becomes greatly in- 

 creased, so that a narrow tube is formed hanging from a conical projection. The 

 latter is the csecum. and the small tube the vermiform appendix. This is the foetal 

 or infantile type (Fig. 652, ^1). It may persist throughout life. Treves found it 



