SURVEY OF CELL-LIFE. 169 



so large a quantity present, that the cells contained in it do 

 not come into contact, as is the case in most cartilages. The 

 chemical and physical properties of the cytoblastema are not 

 the same in all parts. In cartilages it is very consistent, and 

 ranks among the most solid parts of the body; in areolar 

 tissue it is gelatinous; in blood quite fluid. These physical 

 distinctions imply also a chemical difference. The cytoblas- 

 tenia of cartilage becomes converted by boiling into gelatine, 

 which is not the case with the blood; and the mucus in which 

 the mucus-cells are formed differs from the cytoblastema of 

 the cells of blood and cartilage. The cytoblastema, external 

 to the existing cells, appears to be subject to the same 

 changes as the cell-contents ; in general it is a homogeneous 

 substance ; yet it may become minutely granulous as the re- 

 sult of a chemical transformation, for instance, in areolar 

 tissue and the cells of the shaft of the feather, &c. As a 

 general rule, it diminishes in quantity, relatively with the deve- 

 lopment of the cells, though it seems that in cartilages there 

 may be even a relative increase of the cytoblastema propor- 

 tionate to the growth of the tissue. The physiological relation 

 which the cytoblastema holds to the cells may be tw r ofold : 

 first, it must contain the material for the nutrition of the 

 cells ; secondly, it must contain at least a part of what remains 

 of this nutritive material after the cells have withdrawn from 

 it what they required for their growth. In animals, the cyto- 

 blastema receives the fresh nutritive material from the blood- 

 vessels; in plants it passes chiefly through the elongated cells 

 and vascular fasciculi ; there are, however, many plants which 

 consist of simple cells, so that there must also be a transmis- 

 sion of nutrient fluid through the simple cells ; blood-vessels and 

 vascular fasciculi are, however, merely modifications of cells. 



Lav)S of the generation of new cells in the cytoblastema. — 

 In every tissue, composed of a definite kind of cells, new cells 

 of the same kind arc formed at those parts only where the 

 fresh nutrient material immediately penetrates the tissue. 

 On this depends the distinction between organized or vas- 

 cular, and unorganized or non-vascular tissues. In the former, 

 the nutritive fluid, the liquor sanguinis, permeates by means 

 of the vessels the whole tissue, and therefore new cells origi- 



