NITROGEN. 159 



Nitrogen is an essential constituent of the body. It enters into com- 

 bination very slowly. The albumen of the egg and the caseine of 

 milk alike afford this element for the growth of the young. The prin- 

 cipal ingredients of the blood, and indeed of every part of the organs, 

 contain 17 per cent, of it, at least. The albumen of wheat, vegetable 

 fibrine, caseine, and gluten contain 15 per cent, of it. The grains, 

 peas, beans, potatoes, cabbage, carrots, turnips, &c. contain portions 

 of it. Nitrogenized food is supposed to be alone capable of conver- 

 sion into blood, and of forming the animal tissues, hence they are call- 

 ed plastic elements of nutrition ; while the non-nitrogenized foods go 

 to the support of respiration, in which their carbon and hydrogen are 

 oxydized, and heat is evolved ; and hence these are called by Liebig 

 the elements of respiration. Of the first are vegetable fibrine, albumen, 

 cassine, and animal flesh and blood ; and of the second are fat, starch, 

 gum, sugar, pectine, wine, beer and spirits. Plants, as we have else- 

 where said, derive their nitrogen from the ammonia of the atmos- 

 phere; and it is probable that animals also derive a small portion from 

 the same source. 



Animals cannot subsist alone on gum, sugar, starch or butter, for 

 when thus fed they die in from 16 to 24 days. Thus a person feeding 

 for a month on potatoes and water, passed a large quantity of urine, 

 and was extremely feeble, but recovered in a short time on being fed 

 with nitrogenized food. It has been said, also, that the English ne- 

 groes, fed on potatoes only, are apt to die of the dropsy, and that the 

 planters found it necessary to allow them milk and bread ; and fur- 1 

 ther, that the Irish, who feed chiefly on potatoes, drink sour milk to ] ..... 

 digest them better. Nitrogenized aliment is not, however, capable 

 alone of supporting life, if we except gluten. Animals taking gela- 

 tine, fibrine and albumen, separately, die with inanition, but a diet of 

 flesh, bones, or of gluten, collectively, afford complete nutrition. In- 

 stances are cited in which life has been prolonged with sugar and also 

 with gum alone, but some other principles were, it is thought, taken 

 in connection with them. 



It is an important fact connected with animal and vegetable physi- 

 ology, and one which may be viewed in connection with the remarks 

 made on vegetable life in a preceding part of this work, that the vege- 

 table organic principles are identical with animal fibrine, albumen 

 and caseine, possessing the same proportions of carbon, hydrogen, 

 oxygen and nitrogen, and also the same relative amount of sulphur, 

 phosphorus and phosphate of lime. The 3 first, fibrine, albumen and 

 caseine compose Proteine from I hold the first place. If, therefore, 

 animal or vegetable proteine be wanting in food, nutrition is arrest- 

 ed, both in graminivorous and carnivorous animals. The food of all, 

 contains nitrogenized matters identical with the constituents of the 

 blood and tissues of the body, and therefore the elements of gum, su- 



