526 Proceedings of Royal Society of Edinburgh. [sess. 
Measured along the inside of the tube, the common opening of 
the bile and pancreatic ducts is found to occur 75 mm. from the 
pylorus, that is, into the second part of the duodenum. Unlike 
the condition in Cercocebus , the jejunum and ileum are exposed as 
soon as the abdomen is first opened ; there being not even the 
great omentum covering them. Before they are disturbed, they 
lie in the form of a triangular mass of coils immediately caudal to 
the transverse colon ; the base of the triangle is on the right side 
(PI. III. fig. 6). The greater hulk of the small intestine is there- 
fore to the right of the mesial plane. 
When the intestine is opened seventeen very prominent Peyer’s 
patches can be counted ; but valvulae conniventes are absent. 
j Ccecum . — In no part of the intestinal canal is the difference 
between Cercocebus and Lagothrix more marked than in the 
caecum. In Lagothrix it is in the form of a wide bent tube, some 
120 mm. in length, which forms a prominent object when the 
abdominal wall is first removed. It lies immediately caudal to 
the triangular mass of small intestine, and may he said to form one 
of the sides of the triangle. Traced from the termination of the 
ileum, there is first a short portion directed obliquely caudalwards. 
Upon this the main part of the caecum is bent at an acute angle, 
and runs obliquely cephalwards and to the left until it almost 
reaches the left abdominal wall. The terminal 50 mm. or so is 
abruptly recurved upon the main portion of the caecum, and so it 
comes to lie dorsal and slightly caudal to it. This apical recurv- 
ature is permanent, that is, the two pieces of the caecum are hound 
together by the peritoneum passing from one to the other.* 
In no part of the caecum are there even faint indications of 
sacculations ; nor is there, in spite of its great length and con- 
siderable volume, any attempt at the formation of a mesocaecum, 
so that it is free to make certain excursions from the position in 
which it is seen in the specimen at present described. Its lesser 
curvature is dorsal in position, and the bend of the recurved apical 
segment is merely an exaggeration of it. 
The ileo-caecal opening is oval in outline, with its long axis 
* This apical recurvature is apparently common in those Cebidae which 
have a long caecum. It is present in Ateles and Nyctipithecus ; but in Cebus , 
where the caecum is short and simple, it does not obtain. 
