98 SOURCE AND ASSIMILATION OF NITROGEN. 



for their increase or renewal. Corn, grass, and all 

 plants, without exception, contain azotized substan- 

 ces.* The quantity of food which animals take for 

 their nourishment, diminishes or increases in the 

 same proportion as it contains more or less of the 

 substances containing nitrogen. A horse may be 

 kept alive by feeding it with potatoes, which contain 

 a very small quantity of nitrogen ; but life thus 

 supported is a gradual starvation ; the animal in- 

 creases neither in size nor strength, and sinks under 

 every exertion. The quantity of rice which an 

 Indian eats astonishes the European ; but the fact 

 that rice contains less nitrogen than any other kind 

 of grain at once explains the circumstance.f 



Now, as it is evident that the nitrogen of the 

 plants and seeds used by animals as food must be 

 employed in the process of assimilation, it is natural 

 to expect that the excrements of these animals will 

 be deprived of it in proportion to the perfect diges- 

 tion of the food, and can only contain it when mixed 

 with secretions from the liver and intestines. Under 

 all circumstances, they must contain less nitrogen 

 than the food. When, therefore, a field is manured 

 with animal excrements, a smaller quantity of matter 



* The late Professor Gorham obtained from Indian corn a substance 

 to which he gave the name Zeine, according to whose analysis it con- 

 tains no nitrogen ; but ammonia has since been obtained from it. 



t According to the analysis of Braconnot {Jinn, de Chim. et de Phys. 

 t. iv. p. 370), this grain is thus constituted. 



Carolina rice. Piedmont rice. 



Water, . . . 5.00 7.00 



Starch, .... 85.07 83.80 



Parenchyma, . . . 4.80 4.80 



Gluten, . . . 3.60 3.60 



Uncrystallizable sugar, 0.29 0.05 



Gummy matter approach- ? q yi n 10 



ing to starch, ) 



Oil, .... 0.13 0.25 



Phosphate of lime, . . 0.13 0.40 



99.73 100.00. With tra- 



ces of muriate of potash, phosphate of potash, acetic acid, sulphur, 

 and lime, and potash united to a vegetable alkali. 



Vauquelin was unable to detect any saccharine matter in rice. — 

 Thomson's Organic Chemistry, p. 883. 



