TYPES OF MAMMALS. 
21 
the right side reserved for the exhibition of recently acquired 
specimens of especial interest) devoted to the Introductory or 
Elementary Morphological Collection, designed to illustrate the 
more important points in the structure of certain types of 
animal and plant life, and the terms used in describing them. 
This has been called the " Index Museum," as it was thought at 
one time that it would form a sort of epitome or index of the 
main collections in the galleries ; but the name does not exactly 
express that into which it has developed. It is really more 
like the general introduction preceding the systematic portion 
of treatises on any branch of natural history. The space being 
limited, the number of specimens is necessarily restricted. In 
examining this collection the visitor should follow each case in 
the usual order of reading a book, from left to right, and should 
carefully study the printed explanatory labels, to which the 
specimens are intended to serve as illustrations. 
The bays on the west side (left-hand on entering the hall) are 
devoted to the Vertebrated Animals, or those possessing a 
"backbone." In Nos. 1. and II, are shown the characters of 
the Mammals, which form the highest modification of this type. 
The wall-cases of 'No. I. contain specimens showing the bony 
framework (internal skeleton) of Mammals. 
In the first case (south side of the recess) will be seen a Bay I. 
complete skeleton of a good example of the class — a Baboon ^^^®^°^g°^ 
Monkey, with all the bones separated, laid out on a tablet, and 
their names affixed to them. Below is a skeleton of the 
same animal articulated, or with the bones in their natural 
relation to each other, and also named. By examining these 
two specimens an idea may be obtained of the general frame- 
work of the bodies of animals of this class. In other parts of 
the case are placed examples of modifications of the skeleton 
to suit different conditions of life. 
1. Man, showing a skeleton adapted for the upright 
position. 
2. A Bat, or flying Mammal, in which, by the great elonga- 
tion of the fingers, the fore-limbs are converted into wings 
(fig. 7), supporting a web of skin stretched between them. 
3. A Sloth, in which the tips of both limbs are reduced to 
mere hooks, by whose aid the creature hangs back-downwards 
