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, and 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 w T e 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-existing 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 



