46 CHEMISTRY AND PHYSICS IN RELATION 



aside the action of chemical, or purely physical forces, should endeavor to 

 account for every process by the aid of the laws of inorganic nature. 



The latter view is the ultimate consequence of a reaction from the previously 

 entertained views. In a period of philosophical physiology not very remote from 

 the present day, every thing was explained by vital force. This theory was next 

 wholly rejected, and the possibility assumed for our being able to trace all vital 

 processes back to physical and chemical causes. " In the living body," thus wrote 

 physiologists forty years since, * there are different laws at work from those which 

 govern inorganic nature. All the processes of the living organism are of a 

 peculiar character." 



In the present day many physiologists, on the contrary, regard these various pro- 

 cesses as similar in character. The evil of both these theories is, that neither 

 then, or now, has any attempt been made to establish, or even to investigate the 

 deviations occurring in the effects of vital force, and in the action of inorganic force, 

 or to determine their similarity and differences. 



The deductions drawn were not based upon a knowledge of the difference, or 

 similarity of their mutual relations, but upon ignorance of these characteristics. 



WHAT IS MEANT BY CHEMICAL FORCE. 



Those philosophers who regard vital processes as effects of inorganic force*, 

 entirely forget that the expression chemical force means nothing more than the 

 quantitative character of different vital indications, and the qualities dependent 

 upon these quantities. The false view taken of the influence of chemistry in ex- 

 plaining vital phenomena arises from one of two erroneous estimates of the science, 

 either depreciating its effects unjustly, or entertaining too exaggerated an idea of 

 its importance. 



RELATIONS OF DEPENDENCE CANNOT BE ESTABLISHED BY 

 A NUMERICAL SYSTEM. 



If a definite connection exist, or be discovered between two facts, it does not 

 fall within the province of chemistry to prove the connection, but simply to trace 

 out and express its numerical character. 



No relation can be established between two facts by means of numbers, if that 

 relation does not exist ; and hence the importance of the numerical system. 



NUMBERS ARE ONLY EXPRESSIONS OF THE RELATIONS OF 



DEPENDENCE. 



Bitter oil of almonds and benzoic acid are, considering their occurrence and 

 properties, two totally different organic combinations. 



A few years since, no mutual relation was even suspected to exist between the 

 two ; but now it is known that oil of bitter almonds becomes solid and crystalline 

 in the air, and that the resulting body is identical in its properties and composition 

 with benzoic acid. The relation between these two bodies is undeniable after 

 this experiment. Observation shows, that in the transition of oil of bitter almonds 

 into benzoic acid, oxygen is taken up from the air, and an analysis of the two 

 firmly established the conversion numerically, and thus explained it as far as would 

 admit of explanation. 



In a similar manner, by the study of the changes which the oxygen exercises 

 upon fousel oil from potato spirit, a definite relation was discovered between this 

 body and valerianic acid, and it was established by numbers, that one bore the 

 same relation to the other, as alcohol to acetic acid. 



CHEMICAL RELATIONS BETWEEN UREA, URIC ACID, ALLANTOIN, 



AND OXALIC ACID. 



The urine of man contains urea, and frequently uric acid : while the urine of 

 Borne animals is deficient in uric acid, and that of others in urea. The quantity 

 of urea in the urine diminishes with the increase of uric acid ; the urine of the 

 foetus of the cow contains allantoin, while in the urine of man. oxalic acid is 



