116 THE GERM THEORY OF DISEASE. 



take into the economy a simple substance, that substance, if not 

 thrown out of physiological activity, by being built into fixed 

 or formed material, must appear, in some form, in the waste 

 products ; and in this instance it is found in the form of urate 

 of potassa and urate of soda ; while the acid with which it was 

 associated, being dependent on its molecular structure for its 

 chemical characters, is destroyed by remoleculization. Its 

 component elements appear, but in other molecular forms. 

 Hence, the effect on the waste product is not different from 

 that which would have been brought about if the alkaline 

 base alone had been taken. This may be stated as a general 

 law for the organic acids combined with the alkaline bases. 



All of the excremeutitious products possess toxic, or poison- 

 ous properties in some degree. If, by the occurrence of acci- 

 dent or disease, urea be retained in the blood of an animal, it 

 soon presents symptoms of toxaemia, and if the accumulated 

 urea is not speedily eliminated, the animal dies. This is a 

 general law of the waste products. No living being can sus- 

 tain life with a large percentage of its waste product retained 

 in its circulation. Neither can a micro-organism continue to 

 grow after a certain amount of its waste products have accu- 

 mulated in the menstruum in which it is placed. Urea may 

 be regarded as the alkaloid of the animal kingdom, and is the 

 analogue of the alkaloids of the vegetable kingdom. 



WASTE PRODUCTS OF PLANTS. 



The consideration of the waste products of the vegetable 

 kingdom is especially difficult, for several reasons : Plants are 

 characterized by the large amount of their formed material, 

 as compared with the food material consumed by them in 

 their processes of vital activity; and therefore, the amount of 

 their waste products actually excreted is proportionately small. 

 In them, however, other means are found for freeing their 



