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. lxxxvi, 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. H£nle, 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 arc developed in the scrum 

 of pus in the same manner that all other cells originate in 

 their cvtoblastema ; the only difference being that in this 



