22 BIOLOGY. [BOOK T. 



Finally there is extracted from the seeds of the leguminous 

 plants a third albuminoidal substance, containing, like gluten, 

 sulphur, and which is called vegetal caseine. 



The last substance which we have to mention is the green 

 matter of plants, chlorophyll. Its physiological agency is 'ex- 

 tremely curious and interesting ; we shall therefore describe it 

 in detail in the course of our expositions. Here it suffices to 

 observe that chlorophyll cannot be placed in the group of the 

 preceding substances, called proteical. Neither phosphorus nor 

 sulphur is found therein. It is composed only of carbon, of 

 hydrogen, of oxygen, of azote, and, what is altogether character- 

 istic, of iron. Its formula, still however requiring consideration, 

 would be C 18 H 9 AzO s + Fe (in indeterminate quantity). 



2. Chemical Composition of Animals. 



In a preceding chapter we have enumerated the fourteen 

 simple bodies entering into the composition of the most complex 

 of organisms, the human organism. 



A glance thrown at this list suffices to show that if the 

 elementary composition is held in view, and the quality of the 

 elements is alone considered, there is almost identity between the 

 vegetal organisms and the animal organisms. But in both kinds 

 of organism these, elementary bodies are aggregated in various 

 combinations, with the exception of azote and oxygen, of which 

 a part is in a state of liberty alike in the animal and the 

 vegetal organisms. 



In every animal organism also we encounter, in a state of 

 intense blending, immediate principles of the three classes. 



The immediate principles of the first class, or mineral 

 principles, penetrate, entirely formed, into the animal economy ; 

 and entirely formed they come forth from it : this is the case 

 with water, azote, certain salts, and so on. 



The principles of the second class are in general hydrocar- 

 bonised ternary compounds such as lactic acid and the lactates, 



