192 PEOFESSOR CHRISTOPHER ADDISON. 



words half-way between the plane CD. and a plane through the 

 anterior superior iliac spines at a spot rather nearer the lateral 

 line than the middle line. 



(B) The Peritoneum at the Ileo-Colic Junction. — The lovjcr 

 end of the Ileum. — The lower end of the ileum occupies a fairly 

 constant position lying over the right psoas muscle, a little 

 below where this muscle comes to form the pelvic brim. It is 

 nearly always directed upwards and outwards, and the mesen- 

 tery, where the ileum overlies the psoas, usually shortens 

 somewhat suddenly, allowing that part of the bowel only a 

 limited movement. Nevertheless in most cases the bowel can 

 be freely moved if dragged upon. This position of the lower 

 end of the ileum is often made firmer by a prominent peritoneal 

 fold passing downwards from beneath the ileum, near where it 

 overlies the inner border of the psoas, to Poupart's ligament. 



With a shorter peritoneum the movements of this part of the 

 ileum become more limited. Sometimes it is bound down 

 completely to the iliac fossa, whilst in other cases it lies in the 

 pelvic cavity with a prolapsed csecum. 



These positions and mobilities from my 40 cases may be 

 summarised as follows : — In 8 cases the lower end of the ileum 

 was firmly fixed in the iliac fossa. 



In 1 case (No. 18) it was held in the iliac fossa by a strong 

 band attached to it some distance from its termination, allowing 

 the terminal part of the bowel a little movement. 



In 20 cases it was freely movable in various positions, and in 

 11 cases more or less so. 



So that in 50 per cent, of the cases it may he said to be freely 

 movable, in 27"5 per cent, to be movable, and in the remaining 22*5 

 per cent, to be fixed. 



In nearly all cases the direction was as described ; its ob- 

 liquity varying somewhat with the position of the caecum. 



In case 8, in which the csecum was in the pelvis, and in which 

 there was an ascending meso-colon, the direction of the lower 

 end of the ileum was downwards. In 4 of the freely-movable 

 cases the lower end of the ileum was wholly within the pelvic 

 cavity with a displaced csecum. 



