16 
CENTRAL HALL. 
hind-limbs entirely absent, their function being performed 
by the tail. The rudimentary pelvic bones are preserved. 
The rest of the case is occupied by details of the skull in 
some of its principal modifications. At the top are diagrams 
of the structure of bone and cartilage as shown by the micro- 
scope. 
In the wall-case on the opposite (north) side of the bay the 
outline of the osteology of mammals is continued by illustrations 
of the structure of the limbs. At the top of the case is a 
diagram showing the correspondence of the hand and the foot 
in their complete typical form, with the names applied by 
anatomists to the different bones. The series of specimens 
below show the principal deviations which actually occur from 
the typical condition, which, as will be seen, is very nearly 
preserved in the human hand. One series shows some of 
the stages of modification for special purpose (specialization) 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 regarded as 
due to inheritance from a common ancestor. 
Skeletons of In a large case at the back of the bay are the skeletons of a 
Horse^^^ man 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, a study of this group will afford not only an 
instructive lesson in comparative anatomy, but may also be 
of practical utility to the artist. 
