THEIR MODE OF ACTION. 403 



neous formation of new compounds which require to 

 be removed from the body by the organs of excre- 

 tion. 



In an adult these excretions do not vary much 

 either in their nature or quantity. The food taken 

 is not employed in increasing the size of the body, 

 but merely for the purpose of replacing any sub- 

 stances which may be consumed by the various 

 actions in the organism; every motion, every mani- 

 festation of organic properties, and every organic 

 action being attended by a change in the material 

 of the body, and by the assumption of a new form 

 by its constituents.* 



But in a child this normal condition of sustenance 

 is accompanied by an abnormal condition of growth 

 and increase in the size of the body, and of each 

 individual part of it. Hence there must be a much 

 larger quantity of foreign substances, not belonging 

 to the organism, diffused through every part of the 

 blood in the body of a young individual. 



When the organs of secretion are in proper action, 

 these substances will be removed from the system; 

 but when the functions of those organs are impeded, 

 they will remain in the blood or become accumulated 

 in particular parts of the body. The skin, lungs, 

 and other organs, assume the functions of the dis- 

 eased secreting organs, and the accumulated sub- 

 stances are eliminated by them. If, when thus 

 exhaled, these substances happen to be in the state 

 of progressive transformation, they are contagious ; 

 that is, they are able to produce the same state of 

 disease in another healthy organism, provided the 

 latter organism is susceptible of their action, — or 

 in other words, contains a matter capable of suffer- 

 ing the same process of decomposition. 



* The experiments of Barruel upon the different odors emitted from 

 blood on the addition of sulphuric acid, prove that peculiar substances 

 are contained in the blood of different individuals; the blood of a man 

 of a fair complexion and that of a man of dark complexion were found 

 to yield different odors ; the blood of animals also differed in this respect 

 very perceptibly from that of man. — L. 



