Domain of Physiology. 247 



bable primary source of the force appearing in the phenomena 

 of vitality. To the gradual manner in which the colloidal 

 changes take place (for they always require time as an ele- 

 ment) may the characteristic protraction of chemico-organic 

 changes also be referred "*. 



Following Graham, Herbert Spencer has noted that plia- 

 bility, elasticity, the power of absorbing water with change of 

 bulk, and the phenomenon of osmosis, the whole of which are 

 well designated by him as showing sensitiveness to external 

 agencies which are mechanical or quasi mechanical — are pos- 

 sessed in common by mineral colloids and by organized sub- 

 stances. These phenomena are examples of that " continuous 

 adjustment of internal relations to external relations " which 

 characterizes organic lifef. When the chemist shall have 

 succeeded by his synthesis in producing a colloidal albuminoid 

 having the same chemical constitution as protoplasm, there is, 

 as Barker has well said, reason to expect that it will exhibit all 

 the phenomena of life which appear in the protoplasmic matter 

 common to plants and animals. 



§ 25. Barker has, in this connexion, asked the important 

 question, What are we to understand by organic life, and 

 what is the true meaning of vital as applied to a function ? % 

 If, with him, we answer, following Kiiss, " Life is all that 

 cannot be explained by dynamics andchemism," we shall find, 

 restricting our inquiries to the animal economy, that a large 

 part of the phenomena commonly called vital, and, as such, 

 included under the head of animal physiology, are dynamic 

 or chemic. The law of the conservation of energy applies as 

 rigidly to a living animal as to a thermic engine; and the 

 amount of work done or of heat evolved is measured by food 

 consumed in the former as it is by the fuel burned in the latter, 

 the energy manifested in both cases being dependent on the 

 oxidation of carbon and hydrogen. Recent inquiries go far to 

 confirm the view that muscular contraction is electrical, and 

 that electrical manifestation in the muscles is, as in our ordi- 

 nary batteries, dependent on chemism. The tendency of late 

 investigations is to bring nervous activity into the same cate- 

 gory; and the electrical nature of capillarity has been shown 

 by Draper and by Lippmann. The animal circulation is a 



* Thomas Graham, * Chemical and Physical Researches/ p. 554, from 

 Philosophical Transactions for 1861, p. 183. 



t Herbert Spencer, ' Principles of Biology," vol. i. part 1, chapters 1 

 and 2. 



\ George F. Barker, Address as President of the American Association 

 for the Advancement of Science, Boston, August 1880. I have in this 

 paragraph closely followed Professor Barkers argument. 



