EXAMPLES OF THE EXPLANATION OF LAWS. 575 



the gaseous products. 6. The exchange of oxygen and 

 carbonic acid in the lungs is not prevented, hut rather 

 promoted, by the intervention of the membrane of the 

 lungs and the coats of the blood vessels between the 

 blood and the air. It is necessary, however, that 

 there should be a substance in the blood with which 

 the oxygen of the air may immediately combine, 

 otherwise, instead of passing into the blood, it would 

 permeate the whole organism ; and it is necessary 

 that the carbonic acid, as it is formed in the capil- 

 laries, should also find a substance in the blood with 

 which it can combine; otherwise it would leave the 

 body at all points, instead of being discharged through 

 the lungs. 



o. The following is a deduction which confirms, 

 by explaining, the old but not undisputed empirical 

 generalization that soda powders weaken the human 

 system. These powders, consisting of a mixture of 

 tartaric acid with bicarbonate of soda, from which the 

 carbonic acid is set free, must pass into the stomach 

 as tartrate of soda. Now, neutral tartrates, citrates, 

 and acetates of the alkalis are found, in their passage 

 through the system, to be changed into carbonates ; 

 and to convert a tartrate into a carbonate requires an 

 additional quantity of oxygen, the abstraction of which 

 must lessen the oxygen destined for assimilation with 

 the blood, and to the quantity of which the vigorous 

 action of the human system is proportional. 



The instances of new theories agreeing with and 

 explaining old empiricisms, are innumerable. All the 

 just remarks made by experienced persons on human 

 character and conduct, are so many special laws, which 

 the general laws of the human mind explain and 

 resolve. The empirical generalizations on which the 



