Formed Constituents of Organisms 



1 "^ »" 

 loo 



Now if a few be selected from the above list it can be stated 

 that formic acid has been detected in pine tips, in the stinging 

 cells of nettles, in the muscle of animals, in some animal secre- 

 tions, and in red ants as the stinging substance, according 

 to older authors. But the more recent researches of Berg- 

 mann {68: 731) show that it may appear in tissues from the 

 algse and fungi upward to the flowering plants where it is fre- 

 quent. In all probability then it may be detected in a wider 

 variety of animal tissues. According to Bergmann acetic acid 

 is of equally wide distribution amongst plants, and, though 

 it is not met with in animals, acetone that occurs pathologically 

 in the blood and in urine is a related substance that on oxida- 

 tion splits up into acetic and formic acids. 



Butyric, valeric, caproic, palmitic, and stearic acids are 

 all common to both organic kingdoms, and in both form reserve 

 food substances. Other of the fatty acids like lauric, myristic, 

 and arachidic seem to be peculiarly vegetable products. It 

 should further be noted that, in the more complex acids of the 

 above list, those which contain an odd number of carbon atoms 

 are not natural but artificial products, so far as known. 



The oils and fats into which the above and related bodies 

 enter in composition appear as rounded, or at times when fatty 

 as almost angular, masses in the cells that store them. In 

 the algse and fungi they occur alike in the vegetative and spore 

 cells; in the Hepaticae they often appear as large dull spherical 

 or oval masses crowding the leaf cells; amongst mosses they 

 are met with in the protonemal threads and in the spores; 

 while in higher groups they become increasingly abundant and 

 varied. But for us at present the important fact is that they 

 may arise at any evolutionary stage in the entire ])lant series. 

 Though our comparative knowledge is more limited, the same 

 seems to be true for the animal series. 



The large grouj) of the amides and amino-acids have variously 

 been regarded biologically as intermediate steps in the elabora- 

 tion of complex albumens from carbohydrates and nitrogen 



