civilised 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. (45. Prof. Montegazza writes to me
from Florence, that he has lately been studying the last molar teeth in
the different races of man, and has come to the same conclusion as that
given in my text, viz., that in the higher or civilised races they are
on the road towards atrophy or elimination.)
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 is extremely long in many of the lower
vegetable-feeding mammals. In the marsupial koala it is actually more
than thrice as long as the whole body. (46. Owen, Anatomy of
Vertebrates, vol. iii. pp. 416, 434, 441.) 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
appendage is a rudiment, we may infer from its small size, and from the
evidence which Prof. Canestrini (47. Annuario della Soc. d. Nat.
Modena, 1867, p. 94.) 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 flattened 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 sometimes the cause of death, of which fact I
have lately heard two instances: this is due to small hard bodies, such
as seeds, entering the passage, and causing inflammation. (48. M. C.
Martins ( De l Unite Organique, in Revue des Deux Mondes, June 15,
1862, p. 16) and Haeckel ( Generelle Morphologie, B. ii. s. 278), have
both remarked on the singular fact of this rudiment sometimes causing
death.)
In some of the lower Quadrumana, in the Lemuridae and Carnivora, as
well as in many marsupials, there is a passage near the lower end of
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