OF THE GLOBULE OR CELL. 9 



contact). But it is not so with the living globule ; the phe- 

 nomenon is more complicated ; thus oxygen excites the blood 

 globule and modifies its form because it penetrates the glob- 

 ule. The epithelium of the intestine, excited by the gastric 

 juice, undergoes a change, but if this continues too long, it 

 becomes more opaque, etc., showing that it has received an 

 addition of substance. 



Let us now turn our attention to those phenomena pre- 

 sented by the globules when under the influence of physical, 

 chemical, and vital excitants. 



Birth of the Globules. No one has really observed the 

 formation of cells in the midst of an amorphous liquid 

 (blastema). 1 



1 The theory of voluntary formation of cells in a fluid more or 

 less amorphous dates as far back as the time of Schleiden and 

 Schwann, 1838, and even now by C. Robin. Schwann called the 

 liquid in which the generation was supposed to take place cytoUas- 

 tema. Raspail compared the formation of the cell in this cytoblas- 

 tema to that of crystals in a liquid which held in solution tne crys- 

 talline substance. Schwann had, however, observed and described 

 the facts of segmentation, but considered these accidental and in 

 no wise general. To-day, and especially since the works of Remak 

 upon the formation of the blood globules (by segmentation) , it is 

 generally admitted, in accordance with the doctrine of Virchow, 

 that every cell comes from some pre-existing cell (omnis cellula a 

 cellula et in cellula). However, the theory of the Blastema or 

 genesis is still defended in France by eminent histologists, by a 

 numerous school, and especially by Charles Robin. Robin's theory 

 of genesis, moreover, differs in many points from the ancient 

 theory of Schwann. Thus, the media in which the genesis occurs, 

 the blastemata (blood, lymph, interstitial fluids) are themselves 

 the products of pre-existing cells in such fashion that the newly 

 formed elements have come from older cells, not indeed directly, 

 but by mediation (substitution) of a liquid. The manner of the 

 production of the theoretical genesis consists in the spontaneous 

 appearance of a nucleus which is surrounded by the thickened 

 blastema; or else the mass of the blastema is divided into globular 

 islets, each of whose centre has a newly formed nucleus. Accord- 

 ing to this the nucleolus, which may be -afterwards formed, is a 

 secondary element, whilst Schwann considers the nucleolus as the 

 point of departure of cellular formations. In brief, formation by 

 genesis occurs under conditions and periods that may be stated in 

 a general way, as follows : 1st, By the formation of male or female 

 ovula* (spermatozoidal cells); 2d, by the formation of the embry- 

 onic tissues by layers of blastoderm; 3d, in the full-grown animal 

 by the production and renewal of the epitheliums and epiderm; 

 4th, and finally, it is to this manner of formation that almost all* 



