ADIPOSE TISSUE. 
183 
in another specimen, taken from a Cockroach , there are 
tubes, also full of oil globules, hut in neither case, 
and not even in the Cephalopoda , is the oil contained in 
adipose cells. 
As soon, however, as we pass the barrier between 
the invertebrate and vertebrate sub-kingdoms, we find 
that even in the lowest members of the class of fishes, 
true adipose cells occur, and all are doubtless aware, 
that in the liver of the Cod, and of many cartilaginous 
fishes, fat exists in the form of oil without any adipose 
tissue ; — in this particular, the liver resembles that of an 
invertebrate animal. If a portion of the liver of a Cod 
be examined, it will be seen, that with the exception of a 
few secreting cells, it is com- 
posed of a mass of oil globules 
of various sizes, as shown in 
Fig. 140 ; but in a specimen 
from the peritoneum of the 
same Cod , a mass of adipose 
cells full of a dark brown 
liquid oil are visible. The 
adipose cells are grouped in 
lobules, and surrounded by 
areolar tissue, which invests the lobules and sup- 
ports the capillaries distributed to the cells. This 
is well exhibited in two preparations, one of the sub- 
cutaneous adipose tissue of a young child, the other of 
the same tissue from an adult, in which the adipose cells 
far exceed those of the child in diameter. 
FIG. 140 . 
Cod. 
