AREOLAR TISSUE. 111 
out any dissection. Most areolar tissue may be distended by 
forcing air into it, and then innumerable cellular spaces are 
seen communicating with each other in it; it is not known 
whether these are produced artificially, or whether they existed 
previously. Areolar tissue also frequently contains fat-vesicles, 
which, accordiig to Gurlt, are surrounded by a thin and 
transparent, but not fibrous, pellicle, often have an hexagonal 
form, and in that respect resemble vegetable tissue. (Gurlt’s 
Physiologie der Haussaiugethiere, p. 19.) In order to become 
acquainted with the relation which these constituent parts of 
areolar tissue bear to the elementary cells, we must refer to 
the formation of the tissue in the foetus. 
If we examine some areolar tissue from the neck, or from 
the bottom of the orbit of a foetal pig measuring three inches 
and a half in length, we shall find it to be a gelatinous substance, 
somewhat more consistent than the vitreous humour of the eye, 
and, in its earliest state, quite as transparent ; as development 
proceeds, however, it becomes more of a whitish colour, and 
loses its gelatinous quality. When examined with the micro- 
scope, small corpuscles of various kinds are seen in greater 
or less numbers; they are not, however, sufficiently numerous 
in a foetus of the size specified to form the entire gelatinous 
substance, but must necessarily be situated in a transparent, 
structureless,' primordial substance of a gelatinous nature, which 
we will for the present call cytoblastema. The whiter this 
substance appears to the unaided eye, the greater is the 
number of corpuscles contained in it; their quantity, there- 
fore, is continually increasing during development, while 
that of the cytoblastema constantly diminishes. As in con- 
sequence of its transparency, the cytoblastema cannot be 
seen, but is only inferred to exist from the circumstance 
that the corpuscles, which are visible under the microscope, 
could not, at the period when they are but few, form the 
entire jelly, and that when moved, it is plainly seen that 
they are held together by some invisible medium, so it is no 
longer possible to convince ourselves of its existence, when the 
corpuscles are very numerous. It is probable, however, that it 
remains between the fibres of the areolar tissue throughout life. 
' Vide note at page 39. 
