12 QUARTERLY JOURNAL. 



point out the difference between organic and inorganic combina- 

 tions. 



The chemist in his laboratory can obtain from starch, gum, al- 

 bumen and other organic matters, the elements of which they are 

 formed : he can separate them into carbon, oxygen, hydrogen and 

 nitrogen, but he cannot by any means within his reach cause the 

 elements again to combine so as to form these organic matters. 

 These matters are formed only in the living plant and under con- 

 ditions which the chemist cannot imitate. 



Thus gum is formed from three elements, carbon, oxygen, 

 hydrogen, united together in certain definite proportions. The 

 chemist can cause these elements to unite in various ways ; the 

 oxygen and hydrogen wnll combine and form water, the oxygen 

 and carbon will form carbonic acid, the carbon and hydrogen will 

 form carburetted hydrogen. But he cannot by any possible means 

 cause the three to combine and form gum. . 



So in the case of organic matters containing four elements, viz., 

 carbon, oxygen, hydrogen and nitrogen. These elements will unite 

 by ordinary chemical processes to form various compounds. The 

 carbon and oxygen will form carbonic acid ; the hydrogen and 

 nitrogen will form ammonia, and these compounds will again unite 

 to form carbonate of ammonia. But this substance is very differ- 

 ent in its properties from albumen, which is/ound in living plants. 

 , These compounds of the three or four simple substances which 

 are formed only in the laboratory of the living plant, and which 

 cannot be reproduced by the chemist from their elements, are 

 called proximate principles. They are very numerous, and it is 

 not necessary here to enumerate them, but for understanding 

 what is to follow, the composition of the most important of them 

 must be known. 



Some of these proximate principles contain only three of the 

 elements I have mentioned, and then these three are always carbon, 

 oxygen and hydrogen. Others contain four elements, and then 

 nitrogen is added to .the abov^ three. The former are called 7ion- 

 nitrof^enizedj the latter nitrogenized principles. This is a most 

 important distinction, and its applications are numerous in vege- 

 table and animal physiology. 



Of the nitrogenized principles there is a class in which the oxygen 

 and hydrogen exist in the proportions to form water, so that they 



