364 Notices of Books. (July, 
The material in the dialyser was next dried and incinerated, and 
the ash analysed for the determination of the phosphoric acid 
and potash. On the other hand, a certain quantity of flour was 
carefully incinerated, and the phosphoric acid and potash were 
determined in the ash. A correction had to be introduced into 
the analysis by diffusion, owing to the colloid mass still holding 
a proportion of diffusible phosphoric acid and potash, depending 
on the relation existing between the volumes of fluid in and out 
of the dialyser.” 
We fear that this process is open to a serious objection. 
Analysis of the material in the dialyser will show not merely the 
phosphoric acid, soluble, though in a colloid state, but also what- 
ever phosphoric acid may exist in a state insoluble in water, 
such as the phosphates of lime and magnesia. Before assuming 
any of the residual phosphoric acid to be in a colloid state, it 
seems necessary to show that it is, in part at least, soluble. 
Passing over the Author’s views on the modifications of the 
nutritive process in phthisis, we come to what may be regarded 
as the final summary of his investigations :—‘“‘ That in Nature 
soluble matter is undergoing a perpetual transformation,—passing 
in rotation from the crystalloid into the colloid, and from the 
colloid into the crystalloid condition. Animal secretions and the 
products of decomposition of animal and vegetable tissues are 
crystalloid, admitting of their ready distribution through land 
and water by a physical process of diffusion. ‘These crystalloid 
substances are transformed into colloids by plants, and used in 
that form as food for animals; and both plants and animals yield 
them back again in their original crystalloid condition. Chloride 
of sodium alone appears to be an exception to this rule.” 
To a very considerable extent this generalisation must be re- 
garded as well founded. The chief constituents of food— 
albumen, fibrin, casein, gelatin, glucose—are undoubtedly colloid. 
Lactose, indeed, which is a truly crystalloid substance, is a 
necessary of life to the young of all mammalian animals. On 
the other hand, the excretions are rich im compounds admittedly 
crystalline. 
La Terre Vegetale. Geologie Agricole. Par STANISLAS MEUNIER, 
Paris: J. Rothschild. 
WE have here a terse, plain, and lucid manual of agricultural 
ceology, with especial reference to the nature and formation of 
the vegetable soil. The main materials of mould—sand, clay, 
lime, and humus—are described, and their functions pointed out. 
Plain instructions are given for a physical analysis of soils, fol- 
lowed by a description of the various types of mould, such as 
the loamy, the clayey, &c 
In the second part the Author explains the formations of soils, 
