Vital Force. 63 



this preparatory branch of knowledge should usurp the position 

 of tlie guiding light in physiological inquiries. In the investi- 

 gation of the laws governing the phenomena of life, the chemist 

 must condescend to present himself as the assistant of the phy- 

 siologist, just as mechanical and physical philosophers appear as 

 the assistants of the chemist when furnishing him with his 

 balance, his furnaces, his electrical, optical, and similar instru- 

 ments of research. To attempt to deal with facts which present 

 themselves in living bodies according to rules derived exclusively 

 from chemical science, would be mere empiricism. It would 

 be a treatment of symptoms, and not a rational practice directed 

 by knowledge of the governing principles. But there is a de- 

 finite order of progress in all these things, and it is inevitable 

 and indispensable that the development and application of 

 chemical science should precede that of physiology. The facts 

 of vegetable and animal life are compounded of physical and 

 chemical phenomena, modified and directed in their operations 

 by a higher guiding power — the vital force ; but under this 

 superintendence the chemical l«ws display themselves in accord- 

 ance with their own universal characteristics ; so that while the 

 laws of physiology cannot be discovered by chemical research 

 alone, it is evidently more advantageous and more rational to 

 investigate and determine the chemical parts of the inquiry freed 

 from the consideration of the complications resulting from the 

 interference of life. 



At certain points, however, in every investigation of living 

 things the chemist finds himself arrested, and this by pheno- 

 mena to which his method of inquiry is inapplicable. He can 

 refer to chemical laws, for example, the changes going on in the 

 substance of living and of decaying, dead plants, but he cannot 

 tell why the same air and water, on one hand, nourish the 

 living stem and enable it to unfold itself continually in new 

 growth, and on the other hand destroy and decompose the fallen 

 trunk from Avhich the living parts of bud and root have been 

 removed. Before we reach this point, moreover, even without 

 advancing our inquiries so far as the chavr/es exhibited in and l)y 

 living structures, simple chemical analysis of the substances 

 forming or contained in plants, cannot be thoroughly and accu- 

 rately performed without a knowledge of the anatomical con- 

 dition, the material l)asis of physiological science. For, as 

 needs scarcely ho said, though the ultimate constituents ol which 

 minerals,- as well as plants and animals, are composed, the 

 primary elements, are the same, or of the same kind, yet, while 

 all lifeless bodies may be studied thoroughly by tracing up their 

 compositions to their chemical elements and their laws ot com- 



