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112 AREOLAR TISSUE. 
This cytoblastema is present in the greatest quantity, and 
therefore most distinctly demonstrable in the jelly which lies 
between the chorion and amnion in the foetus of the pig at a 
somewhat more advanced period, end where it may be rendered 
very clearly perceptible on the margin of the preparation by 
colouring it with iodine. It is quite as evident in the cellular 
tissue of the young tadpole. An indistinct fibrous appearance 
is sometimes given to it by drawing it asunder; but a fibrous 
structure must not be inferred from that fact simply, since all 
tenacious matter assumes that appearance under similar cir- 
cumstances. Since the number of the corpuscles in the cyto- 
blastema continually increases as development proceeds, it 
would appear that the cytoblastema must be regarded as the 
primary formation, so that we may suppose some of it to be 
first present, and then the corpuscles originate in it; at the 
same time, however, new cytoblastema is formed, in which new 
corpuscles are in like manner generated, whilst the formation 
of those in the previously-existng cytoblastema proceeds 
simultaneously. 
Three kinds of these corpuscles may be distinguished in the 
mammalian embryo; one, which is developed at an earlier 
period than the rest, and is found in all the areolar tissue 
throughout the foetus, and two others, which are formed 
subsequently, and, as it would seem, do not occur in the areolar 
tissue of some parts. We shall, therefore, designate the first 
(which is the only essential kind) proper corpuscles of areolar 
tissue, or—in accordance with the signification which will 
shortly be determined for them—fibre-cells of areolar tissue ; 
the second kind are fat-cells ; the third form round cells of 
areolar tissue, the precise signification of which I have not yet 
been able to make out. 
a. Proper corpuscles of areolar tissue, or fibre-cells of areolar 
tissue. The areolar tissue is not found in the same stage of 
development in every part of the same foetus. When some of 
the tissue that has reached about its middle stage of develop- 
ment is removed from the neck of a pig’s foetus, measuring 
from four to seven inches in length, and examined with the 
microscope, a quantity of corpuscles of various forms are ob- 
served in it. The majority of them, however, appear as they 
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