120 DEVELOPMENT OF CELLS. 



developed coincidently. For, in the embryonic cartilage of the toad, in 

 which this mode of development occurs, Vogt never could detect either 

 free nuclei or cells unprovided with nuclei ; when nuclei were found, they 

 were invariably surrounded by a cell-wall, and when cells were found, they 

 invariably enclosed a nucleus. In explanation of this coincident forma- 

 tion of cell- wall and nucleus, Vogt suggests that probably one portion 

 of the granular matter of the cytoblastema, from which a cell is about to 

 be developed, may collect, centripe tally, at the centre, to form a nucleus, 

 while another portion may collect around, at some distance from it, by a 

 centrifugal influence, and there form a cell-wall. 



Kb'lliker's * opinion of the mode of origin of cells, founded upon the 

 results of researches on the development of invertebrate animals, differs in 

 several respects from those entertained by Henle and Vogt. For he 

 believes that the so-called primary cell is, as Schleiden and Schwann 

 described, in almost all cases developed around a nucleus, which persists 

 for a greater or less length of time, and that the nucleus also is in most 

 cases formed around a nucleolus. The irregular appearance frequently 

 presented by the nucleus of pus-corpuscles, especially after being acted 

 upon by dilute acetic acid, is not, as Henle supposed, an early character, 

 and an indication of its being originally composed of two or more separate 

 particles for, at its first formation, the nucleus is invariably a simple 

 vesicular body but is an after effect, and is due to the nucleus being 

 divided into two or more new vesicular bodies, each of which may, if 

 carefully examined, be seen to contain a minute particle or nucleolus; 

 and these, he thinks, originate by endogenous multiplication. 



In a recent essay, H. Miiller \ has advanced an opinion concerning the 

 development of the corpuscles of pus and of chyle, which differs from 

 that of other writers, and from which it would seem that these corpuscles 

 originate in a manner somewhat similar to the third mode of development 

 described by Vogt. He believes that previous to the development of cells 

 the chyle consists of a number of particles, some of which are soluble, 

 others insoluble. In the production of chyle-corpuscles or cells, a num- 

 ber of both kinds of particles become aggregated into a mass; shortly 

 after the formation of which, the insoluble particles collect together in 

 the centre to form the nucleus, while the soluble ones dispose themselves 

 around the circumference, and are transformed into the cell-wall. A 

 very similar process he states to be pursued in the formation of pus- 

 corpuscles. 



Such are some of the principal observations which have been lately 

 made on the subject of the development of cells. The amount might 

 have been considerably extended by including the remarks of many other 



* Entwickelungs-geschichte der Cephalopoden, 1844, p. 142. 



t Beitriige zur Morphologic des Chylus und Eiters, in Henle und Pfeufer's Zeitschrift, 

 b. iii. 



