THE ACTIVE FORCES OF LIVING ORGANISMS 29 



the rate and degree of oxidation, it is very evident 

 that the amount of oxygen contained in them in 

 proportion to the other elements, and perhaps espe- 

 cially to nitrogen, is of considerable importance. 

 Indeed, the degree of oxidation of all vegetal products 

 is probably one of the chief factors, though, of course, 

 not the only one, in the determination of their 

 chemical characteristics and physiological effects. 

 Bitters and alkaloids in general may be said to 

 produce in the first instance an astringent or con- 

 stricting effect on the tissues with which they come 

 in contact. Whether or not this result leads to a 

 diminution, or to an increase, of oxidation depends 

 on the condition of the tissues previously in respect 

 to contraction or relaxation, and this naturally applies 

 in the case of strychnine ; but it is certainly true that 

 the more any tissue is contracted, the less easily does 

 oxidation in it take place. The action, however, of 

 drugs which produce constriction of the tissues, and 

 so diminish oxidation, is probably always followed 

 by a reaction in the opposite direction, which varies 

 very considerably in different cases, depending partly 

 on the chemical composition of the alkaloid or bitter 

 employed, and partly on the physiological condition 

 of the person taking it. There are, indeed, certain 

 generSfl truths connected with the action of all drugs 

 which one may express as follows : 



All drugs influence the rate and intensity of the 

 oxidation of the tissues both by their action and by 

 their reaction. 



