THE PRINCIPLE OF VITAL AFFINITY. 169 



(10 H 0) starch is produced, 12 C 10 II 10 0, 24 of oxygen passing off." — {Chemistry 

 of Vegetable and Animal Physiology, p. 67).* 



But it is important to fix our attention, for a short time,on the instances 

 adduced by Mulder, of the formation of starcli, 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, vegetable and animal, is 

 still essentially dependent ; and because the simplicity of the process makes it a fit 

 case for considering the question, whether the power here named is strictly en- 

 titled to the epithet vital ; or whether, as some eminent physiologists in this 

 country maintain, the idea expressed by that term is incorrect and unscientific. 



The opinion of those who oppose the doctrine of vital afiinity, is thus dis- 

 tinctly stated in the Anatomy of Drs Quain and Shaepey : 



" Although the products of chemical changes in living bodies for the most 

 part differ from those appearing in the inorganic world, the difference is never- 

 theless to be ascribed, not to a peculiar or exclusively vital affinity different from 

 ordinary chemical aflftnity, but to common chemical affinity, operating in circum- 

 stances or conditions which present themselves in living bodies only ; and un- 

 doubtedly the progress of chemistiy is daily adding to the probability of this 

 view." 



I consider this to be a hasty and ill advised statement ; and to shew this, I 

 request attention, first, to the perfect simplicity of the apparatus by which this 

 change is effected. " In all plants," says Muldee, " there exists a small organ, 

 of the most simple form, although employed by nature for the most varied pur- 

 poses. It is a small filmy sac, a thin membrane, which encloses a small space, 

 which it enables to communicate with the exterior space through invisible pores. 

 These little sacs or cells are the chief organs of plants. A countless multitude 

 of them, grouped together, forms the whole bulk of the plant, so that if every thing 

 except the cells be destroyed, the shape and size of the plant are not in the least 

 changed or diminished." 



Into this simple apparatus in certain parts of plants, water, impregnated with 

 carbonic acid, is introduced, whUe the plants exhibit the phenomena of life ; and 



* 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, 

 apphed to any material substance, has a more general meaning, as simply the cause of change of any 

 kind, and is therefore appUcable where the result of the property ascribed to any substance may be very 

 different from visible motion. 



VOL. XVl. PART II. 2 tr 



