Chap. I. 
RUDIMENTS. 
27 
iised men habitually feeding on soft, cooked food, and 
thus using their jaws less. I am informed by Mr. Brace 
that it is becoming quite a common practice in the United 
States to remove some of the molar teeth of children, 
as the jaw does not grow large enough for the perfect 
development of the normal number. 
With respect to the alimentary canal I have met 
with an account of only a single rudiment, namely the 
vermiform appendage of the caecum. The caecum is 
a branch or diverticulum of the intestine, ending in a 
cul-de-sac, and it is extremely long in many of the 
lower vegetable-feeding mammals. In the marsupial 
kaola it is actually more than thrice as long as the 
whole body . 34 It is sometimes produced into a long 
gradually-tapering point, and is sometimes constricted 
in parts. It appears as if, in consequence of changed 
diet or habits, the caecum had become much shortened 
in various animals, the vermiform appendage being left 
as a rudiment of the shortened part. That this ap- 
pendage is a rudiment, we may infer from its small 
size, and from the evidence which Prof. Canestrini 35 has 
collected of its variability in man. It is occasionally 
quite absent, or again is largely developed. The passage 
is sometimes completely closed for half or two-thirds of 
its length, with the terminal part consisting of a flat- 
tened solid expansion. In the orang this appendage is 
long and convoluted : in man it arises from the end of 
the short caecum, and is commonly from four to five 
inches in length, being only about the third of an inch 
in diameter. Not only is it useless, but it is some- 
times the cause of death, of which fact I have lately 
heard two instances : this is due to small hard bodies, 
34 Owen, * Anatomy of Vertebrates/ vol. iii. pp. 416, 434, 441. 
35 4 Annnario della Soc. d. Nat/ Modena, 1867, p. 94. 
