28 
CENTRAL HALL. 
tlie typical condition, which,, as will be seen, is very nearly 
preserved in the human hand. One interesting series shows 
some of the stages of modification for special purpose (specializa- 
tion) by which a typical five-fingered hand becomes converted 
into that of the single-fingered Horse, and another series ends with 
the hand of the ruminants, with only two fingers remaining, some- 
times, but erroneously, called a " cloven hoof." Similar changes 
are shown in the toes of the hinder extremity, illustrating the 
same common plan running through infinite modifications in 
detail, enabling the organ to perform such a variety of purposes, 
and to exhibit such diversity of outward appearance. The 
existence of this common plan is now generally thought to be 
due to inheritance from a common ancestor. 
Mankind °' ^ large case at the back of the bay are the skeletons of a 
Horse. i^an and of a horse, arranged for comparison with each other, 
and also to show the position of the bones of both in relation to 
the external surface. In the case of the horse, the skin of the 
same animal from which the skeleton was prepared was care- 
fully mounted, and, when dry, divided in the middle line, and 
one half, lined with black velvet, placed behind the skeleton. 
In the man the external surface is shown by a papier-mache 
model, similarly lined and placed in a corresponding position. 
As all the principal bones of both skeletons have their names 
attached to them, a careful study of this group affords not only 
an instructive lesson in comparative anatomy, but will also, it 
is hoped, be of practical utility to the artist. 
Teeth of The central case of the bay contains a collection illustrat- 
MammaiB. ^-^^ principal characters of the teeth in the Mammalia. 
Its inspection should commence at the north-east corner, where 
the visitor will find himself after completing the survey of the 
osteological specimens in the wall-cases. In the first division 
specimens are placed showing the general characters of 
teeth, their form, the different tissues of which they are 
composed, the two great types of dentition in mammals, 
homodont and heterodont, the nomenclature and homologies of the 
different teeth, and their development and succession. The 
principal modifications of teeth according to their function are 
next shown by examples of forms adapted for fish-eating, flesh- 
eating, insect-eating, grass-eating, &c. The remainder of the 
