56 



ANIMAL CHEMISTRY. 



tions contain nitrogen chemically combined. 

 They pass into fetid putrefaction, and yield 

 either in this change, or in the dry distillation, 

 ammoniacal products. Even the saliva, 

 when acted upon by caustic potash, disen- 

 gages ammonia freely. 



84. Medicinal or remedial agents may be 

 diviued into two classes, the nitrogenized 

 and the non-nitrogenized. The nitrogenized 

 vegetable principles, whose composition 

 differs from that of the proper nitrogenized 

 elements of nutrition, also produced by a 

 vegetable organism, are distinguished, be- 

 yond all others, for their powerful action on 

 fine animal economy. 



The effects of these substances are singu- 

 larly varied ; from the mildest form of the 

 action of aloes, to the most terrible poison, 

 strychnia, we observe an endless variety of 

 different action. 



With the exception of three, all these 

 substances produce diseased conditions in 

 the healthy organism, and are poisonous in 

 certain doses. Most of them are, chemi- 

 cally speaking, basic or alkaline. 



No remedy, devoid of nitrogen, possesses 

 a poisonous action in a similar dose.* 



85. The medicinal or poisonous action of 

 the nitrogenized vegetable principles has a 

 fixed relation to their composition ; it can- 

 not be supposed to be independent of the 

 nitrogen they contain, but is certainly not in 

 direct proportion to the quantity of nitrogen. 



Solanine (38,) and picrotoxine (39,) which 

 contain least nitrogen, are powerful poisons. 

 Q,uinine (40) contains more nitrogen than 

 morphia (41.) Caffeine (42,) and theobro- 

 mine the most highly nitrogenized of all 

 vegetable principles, are not poisonous. 



86. A nitrogenized body, which exerts, 

 by means of its elements, an influence on 

 the formation or on the quality of a secre- 

 tion', must, in regard to its chemical charac- 

 ter, be capable of taking the same share as 

 the nilrogenized products of the animal body 

 do in the formation of the bile ; that is, it 

 must play the same part as a product of the 

 vital process. On the other hand, a non- 

 azotized medicinal agent, in so far as its ac- 

 tion affects the secretions, must be capable 

 of performing in the animal body the same 

 part as that which we have ascribed in the 

 formation of the bile, to the non-azotized 

 elements of food. 



Thus, if we suppose that the elements of 

 hippuric or uric acids are divided from the 

 substance of the organs in which vitality 

 resides ; that as products of the transform- 

 ation of these organs they lose the vital 

 character, without losing the capacity of 

 undergoing changes under the influence of 

 the inspired oxygen, or of the apparatus of 

 secretion ; we can hardly doubt that similar 



* This consideration or compnraiive view has 

 led lately to a more accurate investigation of the 

 composition of picrotoxine, the poisonous principle 

 of cocculus indicus ; and M. Francis has disco 

 vered the existence of nitrogen in it, hitherto over- 

 looked, and has also determined its amount. 



nitrogenized compounds, products of the 

 vital process in plants, when introduced into 

 the animal body, may be employed by the 

 organism exactly in the same way as the 

 nitrogenized products of the metamorphosis 

 of the animal tissues themselves. If hippu- 

 ric and uric acids, or any of their elements, 

 can take a share, for example, in the form- 

 ation and supply of bile, we must allow the 

 same power to other analogous nitrogenized 

 compounds. 



We shall never, certainly, be able to dis- 

 cover how men Avere led to the use of the 

 hot infusion of the leaves of a certain shrub 

 (tea) or of a decoction of certain roasted 

 seeds (coffee.) Some cause there must be, 

 which would explain how the practice has 

 become a necessary of life to whole nations. 

 But it is surely still more remarkable, that 

 the beneficial effects of both plants on the 

 health must be ascribed to one and the same 

 substance, the presence of which in two 

 vegetables, belonging to different natural 

 families, and the produce of different quar- 

 ters of the globe, could hardly have presented 

 itself to the boldest imagination. Yet recent 

 researches have shown, in such a manner as 

 to exclude all doubt, that caffeine, the pecu- 

 liar principle of coffee, and theine, that of 

 tea, are, in all respects, identical. 



It is not less worthy of notice, that the 

 American Indian, living entirely on flesh, 

 discovered for himself, in tobacco smoke, a 

 means of retarding the change of matter in 

 the tissues of his body, and thereby of mak- 

 ing hunger more endurable; and that he 

 cannot withstand the action of brandy, 

 which, acting as an element of respiration, 

 puts a stop to the change of matter by per- 

 forming the function which properly belongs 

 to the products of the metamorphosed tis- 

 sues. Tea and coffee were originally met 

 with among nations whose diet is chiefly 

 vegetable. 



87. Without entering minutely into the 

 medicinal action of caffeine, (theine,) it will 

 surely appear a most striking fact, even if 

 we were to deny its influence on the pro 

 cess of secretion, that this substance, with 

 the addition of oxygen and the elements of 

 water, can yield taurine, the nitrogenized 

 compound peculiar to bile: 



1 at. caffeine or theine=C 8 N 2 H 5 O 2 

 9 at. water - = H 9 O 9 

 9 at. oxygen - = O 9 



=2 at. taurine - = 2(C 4 NH 7 O 10 ) 

 A similar relation exists in the case of the 

 peculiar principle of asparagus and of al , 

 thaea, asparagine ; which also, by the addi- 

 tion of oxygen and the elements of water, 

 yields the elements of taurine. 



1 at. asparagine = C 8 N 2 H 8 O 6 

 6 at. water = H 6 O 6 



8 at. oxygen = O 8 



C 8 N 2 H' 4 To = 



= 2 at. taurine =(C 4 NH 7 O 10 



The addition of the elements ol water and 



