86 PHILOSOPHY OF ZOOLOGY. 
pine, to assist in rolling up the body and moving the spmes, 
and in birds, in the erection of their feathers. In man, it 
can scarcely be said to exist, unless in the upper parts, 
where cutaneous muscles may be observed, destined for 
moving the skin of the face, cheeks and head. In the 
skin of the frog, the only cutaneous muscles which can be 
observed, are seated under the threat ; the skin on the other 
parts of the body being loose and unconnected with the 
parts beneath, 
The use of this layer of the tegument, is to corrugate 
the skin, and elevate the hairs, feathers or spines with which 
it is furnished. 
5. Cellular web.—This forms the mnermost layer of the 
common integuments, and rests immediately on the flesh 
of the body. It consists of plates crossing one another in 
different directions, and forming a cellular membrane, va- 
rying in its thickness, tenacity and contents, according to 
the species. In frogs it does not exist. The cells of this 
membrane are filled with various substances, according to 
the nature of the animal. In general, they contain fat, as 
in quadrupeds and birds. In some of these, the layer is in- 
terrupted, as in the ruminating animals, while it is conti- 
nuous in others, as the boar and the whale. In birds, 
while a part of this web is destined for the reception of fat, 
other portions are receptacles for air. In the moon-fish, 
the contamed matter resembles albumen in its chemical 
characters. 
Where this layer of subcutaneous fat is of considerable 
thickness, the sensibility of the skin above is greatly dimi- 
nished. Hence, it is considered as destined to weaken the 
impressions of external injuries, and to protect against the 
effect of the changes of temperature in the surrounding ele- 
ment. But it is subservient to more important purposes in 
the animal economy. The cells are the magazines, mto 
