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- 
tema 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 twofold: 
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of this nutritive material after the cells have withdrawn from 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. 
Laws 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 are 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- 
