AREOLAR TISSUE. 119 
most of them being much larger than the fibre-cells, and some 
as large as the largest adipose cells. They can very rarely 
be seen without the aid of the most favorable light, but when, 
under such circumstances, the observer has once detected one 
of them, and become familiar with the degree of its trans- 
parency, they may be recognized in great numbers. They 
have a distinct nucleus attached to the internal surface of their 
wall, contaiming one or two nucleoli. The nucleus always 
attracts attention first ; the cell surrounding it is either quite 
transparent, and void of granules, or has granulous contents, 
and this granulous deposit is first formed in the neighbourhood 
of the nucleus, the remaining portion of the contents being 
still transparent. (See the figure.) Gradually, the entire con- 
tents appear to become granulous. These cells are distinguished 
from the fibre-cells of areolar tissue by the circumstance of 
their becoming much larger than the latter, and their not 
being elongated into fibres, and from the adipose cells, in that 
they do not contain fat. I have found them in areolar tissue 
taken from the bottom of the orbit, and from the neck of a 
foetal pig, but do not know whether they occur in the areolar 
tissue of all parts of the body; nor can I determine their sig- 
nification. They might be regarded as cellular spaces which 
had been produced by the distension of the areolar tissue with 
air. In such case, they must communicate with one another 
in the course of their further development. But this appears 
to me to be somewhat improbable ; and those spaces may be 
merely artificial productions. I should rather regard the cells in 
question as a modification of the adipose cells. For since, ac- 
cording to Gurlt, the ordinary adipose cells in the adult may 
contain mere watery fluid, one may also conceive the cells 
destined to the formation of fat becoming completely developed, 
without that formation actually taking place within them. 
There are, indeed, adipose cells which contain fat even in the 
earliest stage of their development, but that is no reason 
why the formation should not take place at a much later period 
in other cells. The granulous deposit in many of them might 
be regarded as the transitional step to the formation of fat. 
The cellular tissue of the foetus differs in its chemical con- 
stitution from that of the adult, since we cannot obtain any 
