66 EVOLUTION AND DISEASE. 
ways :—The communication with the caecum may 
become obliterated, and the tube distend into a cyst 
in consequence of fluid accumulating within it ; such a 
cyst may rupture, and lead to minor troubles, as local 
inflammation or abscess, or induce death by peritonitis. 
Adenoid, or lymphatic, tissue is very prone to ulcerate, 
and under certain conditions the adenoid tissue lining 
the appendix may inflame and lead to fatal perforation. 
A much commoner danger is the entrance into it of such 
things as fruit-stones and similar indigestible sub- 
stances taken with the food; these 
act as irritants, and in the long run 
destroy life. A somewhat similar 
condition of things may be studied 
in lions and tigers. In these hand- 
some animals there is no vermiform 
appendix, and the caecum is even — 
more vestigial than in man. This 
Fic. 33-—The vermilorm small caecum occasionally contalam 
appendix of a Silvery 
Gibbon (Hylobates leu- a concretion having a fragment of | 
ane bone, a nail, or piece of wood for the © 
nucleus. Concretions in the vestigial cacum of the — 
tiger produce similar effects to cherry-stones, &c., in — 
the human vermiform appendix, and on two occasions I 
have been able to connect such concretions with the | 
fatal illness of tigers. | 
Although a small and insignificant cecum is not 
always an advantage, it is on the other hand a disad- 
vantage to have one too large. The horse will illustrate | 
this: it has a caecum measuring, on an average, one | 
metre in length, and a capacity equal to thirty-five litres 
