Dr Alison on the Principle of Vital Affinity. 137 



he uses language in regard to the nature and results of che- 

 mical changes in living bodies, which seems to me vague and 

 speculative, and even inconsistent with what he had stated 

 in the passages just quoted, e, g., when he says that " the 

 ultimate causes of the different conditions of the vital force in 

 nutrition, reproduction, muscular motion, &c., are chemical 

 forces.^' — {Organic Chemistry, p. 10.) 



The following sentence by Mulder expresses the very same 

 idea, although it might be thought, from the manner in which 

 this author expresses himself against any introduction of the 

 vital principle in this department of physiology, that he con- 

 siders all the chemical changes in living structures to be re- 

 ferable to the same laws as in inorganic matter. 



" By a small organ of a plant a force is exercised, exciting 

 forces which slumbered in the carboji, oxygen, and hydrogen, 

 or rather modifying the forces which existed in these, so that 

 12 equivalents of carbon unite with 10 of hydrogen and 10 of 

 oxygen ; and from 12 equivalents of carbonic acid (12 C Og) 

 and 10 of water (10 H 0) starch is produced, 12 C 10 H 10 0, 

 24 of oxygen passing oflf." — (Chemistry of Vegetable and Ani- 

 mal Physiology, p. 67 )* 



But it is important^o fix our attention, for a short time, 

 on the instances adduced by Mulder, of the formation of 

 starch, or some of its allied compounds, out of carbonic acid 

 and water, by the combination of the carbon of the acid with 

 the elements of water, and the expulsion of the oxygen of the 

 acid; because this is the grand and fundamental power, 

 which must have been called into operation when organized 

 structures were first created on earth, and on the continued 

 exercise of which the existence of all such structures, vege- 



* In the foregoing and other translations from recent German writers, the 

 word force is used in a sense which I think would be much better expressed by 

 the term power or property, merely on this account, that the English word force, 

 in physical discussions, has usually a precise and limited meaning assigned to 

 it, as a cause capable of producing visible motion, and of which we have a 

 measure, either in the velocity or in the quantity of motion which it can excite ; 

 whereas the term power or property, applied to any material substance, has a 

 more general meaning, as simply the cause of change of any kind, and is there- 

 fore applicable where the result of the property ascribed to any substance may 

 Be very different from visible motion. 



