182 
HISTOLOGY OF ANIMALS. 
'/ l W^—F/^vV . "-'jKS, 
Cells of adipose tissue. 
fig. 139 . pressure as in Fig. 139, they 
are, like vegetable cellular 
tissue, of a more or less dode- 
cahedral shape. In the young 
subject, they vary in diameter 
from ^th to ^th, and in the 
adult, they are rarely smaller 
than ^th of an inch. When 
first developed in the embryo, 
they have a nucleus, but this very soon disappears. 
Adipose tissue exists in the form of lobules, which 
may occur singly or in masses of many pounds’ 
weight. A certain amount of it is considered a sign 
of health, but an excess, especially if it be in one 
mass, as in certain tumours, constitutes disease. 
In all works on anatomy and physiology, even of so 
late a period as last year, it is distinctly stated, that 
adipose tissue exists in invertebrate animals ; this, how- 
ever, I find to be incorrect, and it cost me no small 
amount of labour to prove it. Fat certainly does exist 
in insects, Crustacea, and mollusca, but no true adipose 
cell is ever present ; it could not be nourished without 
its accompanying blood-vessels, and these are not found 
in invertebrata. The tissue resembling adipose tissue 
usually belongs to the liver or other glandular organ, 
and the fat exists in its cells in the form of oil. 
In the liver of the larva of a Goat Moth , Cossus 
ligniperda , which consists of a series of cells or vesicles, 
containing a large number of globules of oil, and again, 
