AREOLAR TISSUE. 121 
by the addition of either of those substances in excess. With 
respect to hydrochloric acid, the result was the same as before 
described. 
It cannot appear at all surprising that the areolar tissue of 
the foetus differs from that of the adult, when it is known that 
many cell-membranes undergo a change in their chemical 
constitution at different stages of their development, and that 
the growth of the cells is not a mere mechanical expansion. 
Previous to quitting the subject of areolar tissue, we must 
consider some other processes, by means of which a new for- 
mation of it takes place in the adult. If (as I have already 
laid down as an axiom in my first essays, Froriep’s Notizen, 
1838, Nos. 91, 103, and 112) the formation of cells be really the 
principle of development of all organic structures, it must apply 
no less to pathological than to physiological processes; and 
that it really does so, is proved by the investigations of Henle 
with reference to the new products resulting from inflammation, 
namely, exudation, suppuration, and granulation; the results of 
his observations are communicated in Hufeland’s Journal, 
vol. Ixxxvi, No. 5. 
Vogel pronounced the pus-corpuscles to be epithelium, in 
consequence of their resemblance to epithelial cells, and there 
was much of probability in the statement, so long as it ap- 
peared that every diversity in the physiological signification 
of an elementary structure was based upon a recognizable 
diversity of formation. But this conclusion lost its importance, 
when I brought forward the formation of cells as the common 
principle of development of elementary structures, which were 
perfectly distinct in a physiological sense, and at the same time 
showed the most opposite tissues to be developed from cells, 
which, in the first instance, perfectly resemble each other, and 
present no distinction either in appearance or in the signi- 
fication of their individual parts. Henle, however, proved a 
positive difference between the epithelial cells and pus-cor- 
puscles, for he found that the nuclei of the youngest epithelial 
cells were not broken down by the action of acetic acid like 
those of the pus-corpuscles. The latter must, therefore, be 
regarded as peculiar cells, which are developed in the serum 
of pus in the same manner that all other cells originate in 
their cytoblastema; the only difference being that in this 
