238 THE AMERICAN MONTHLY (Sep 
Ist. Renovation of the surfaces of contact between the 
oxidisable parts and the external oxygen. More effective 
elimination of carbon dioxide.t 
2nd. Conveyance of the nutritive particles and resi- 
dues. Nutrition of the masses of alveolar protoplasm, 
which fulfill the functions of glands, etc., according to 
principles of Van’t Hoff, Becquerel,{ and Loeb. Cireula- 
tion of the reserves and circulation in the zymoses. 
3rd. Deposition of certain materials and separation of 
some others according to their solubility, density, and so 
forth. Concentric formations, incrustations, ete. 
The study of these internal currents is, one may say, 
the chief aim of physiology. They may be explained in 
terms of known physico-chemical causes rather than by 
an undiscovered and undiscoverable vital force. The 
causes are— 
A. Diffusion and osmotic currents. 
B. Heat. Oxidations. 
C. Ingestion of the materials that support the pheno- 
mena of diffusion and oxidation. 
D. Partial vacua and changes of every kind in internal 
pressure, induced by evaporation, ete. | 
The action of these causes may be tested by both the 
natural and the synthetic protoplasm. | 
A. The use of gummy water is indispensable if one 
wishes to observe the circulation of protoplasm in the 
elements of trees, and the movements are generally de- 
pendent on the conditions of diffusion (cf. Butschli’s 
foams).* The currents of the artificial product vary in 
accordance with diffusive power of the substances, the 
quantity of liquid, and the presence of some large granu- 
lations. 
+See A. L. Herrera and D, Vergara Lope, ‘‘ New Theory of Respira- 
tion.’”’ Congress at Moscow, 1898. 
t Becquerel, ‘‘Les forces electro-capillaires dans les phenomenes de 
nutrition.’”’ Comptes rendus Acad. Sct. Paris, 16 Fevrier 1875, 
*See Milne-Edwards, ‘‘Anatomie et physiologie comparee.”’ 
