52 



ANIMAL CHEMISTRY. 



while we cjnnot tell in what precise wa 

 they are so employed. 



By the action of caustic alkalies allan 

 toine may be resolved into oxalic acid an 

 ammonia ; the same products are obtaine( 

 when oxamide is acted on by the same re 

 agents. Yet we cannot, from the similarity 

 of the products, conclude that these two 

 compounds have a similar constitution. In 

 like manner the nature of the products 

 formed by the action of acids on choleic acic 

 does not entitle us to draw any conclusior 

 as to the form in which its elements are 

 united together. 



63. If the problem to be solved by or- 

 ganic chemistry be this, namely, to explain 

 the changes which the food undergoes in the 

 animal body ; then it is the business of this 

 science to ascertain what elements must be 

 added, what elements must be separated, in 

 order to effect, or, in general, to render possi- 

 ble, the conversion of a given compound into 

 a second or a third ; but we cannot expect 

 from it the synthetic proof of the accuracy oi 

 the views entertained, because every thing 

 in the organism goes on under the influence 

 of the vital force, an immaterial agency, 

 which the chemist cannot employ at will. 



The study of the phenomena which ac- 

 company the metamorphoses of the food in 

 the organism, the discovery of the share 

 which the atmosphere or the elements of 

 water take in these changes, lead at once to 

 the conditions which must be united in 

 order to the production of a secretion or of 

 an organized part. 



64. The presence of free muriatic acid in 

 the stomach, and that of soda in the blood, 

 prove beyond all doubt the necessity of com- 

 mon salt for the organic processes ; but the 

 quantities of soda required by animals of 

 different classes, to support the vital pro- 

 cesses, are singularly unequal. 



If we suppose that a given amount of 

 blood, considered as a compound of soda, 

 passes, in the body of a carnivorous animal, 

 in consequence of the change of matter, 

 into a new compound of soda, namely, the 

 bile, we must assume, that in the normal 

 condition of health, the proportion of soda 

 in the blood is amply sufficient to form bile 

 with the products of transformation. The 

 soda which has been used in the vital pro- 

 cesses, and any excess of soda must be ex- 

 pelled in the form of a salt, after being sepa- 

 rated from the blood by the kidneys. 



Now, if it be true, that, in the body of 

 an herbivorous animal, a much larger 

 quantity of bile is produced than corre- 

 sponds to the amount cf blood formed or 

 transformed in the vital processes; if the 

 greater part of the bile, in this case, pro- 

 ceeds from the non-azotised constituents of 

 the food, then the soda of the blood which 

 has been formed into organized tissue (as- 

 similated or metamorphosed) cannot possi- 

 bly suffice for the supply of the daily secre- 

 tion of bile. The soda, therefore, of the 

 bile of the herbivora must be supplied di- 



rectly in the food; their organism must pos 

 sess the power of applying directly to the 

 formation of bile all the compounds of soda 

 present in the food, and decomposable by 

 the organic process. All the soda of the 

 animal body obviously proceeds from the 

 food, but the food of the carnivora contains, 

 at most, only the amount of soda necessary 

 to the formation of blood ; and in most cases, 

 among animals of this class, we may as- 

 sume that only as much soda as corresponds 

 to the proportion employed to form the 

 blood is expelled in the urine. 



When the carnivora obtain in their food 

 as much soda as suffices for the production 

 of their blood, an equal amount is excreted 

 in the urine ; when the food contains less, a 

 part of that which would otherwise be ex- 

 creted is retained by the organism. 



All these statements are most unequivo- 

 cally confirmed by the composition of the 

 urine in these different classes of animals. 



65. As the ultimate product of the changes 

 of all compounds of soda in the animal body, 

 we find in the urine the soda in the form of 

 a salt, and the nitrogen in that of ammonia 

 or urea. 



The soda in the urine of the carnivora is 

 bund in combination with sulphuric and 

 phosphoric acids j and along with the sul- 

 Dhate and phosphate of soda we never fail 

 ;o find a certain quantity of a salt of ammo- 

 nia, either muriate or phosphate of ammonia. 

 There can be no more decisive evidence in 

 avour of the opinion, that the soda of their 

 )ile or of the metamorphosed constituents of 

 heir blood is very far from sufficing to neu- 

 ralize the acids which are separated, than 

 he presence of ammonia in their urine. 

 Phis urine, moreover, has an acid reaction. 



In contradistinction to this, we find, in 



he urine of the herbivora, soda in pre- 



lominating quantity; and that not combined 



with sulphuric or phosphoric acids, but 



with carbonic, benzoic, or hippuric acids. 



65. These well established facts demon- 

 trate that the herbivora consume a far larger 

 juantity of soda than is required merely for 

 tie supply of the daily consumption of blood, 

 n their food are united-all the conditions for 

 tie production of a second compound of soda, 

 estined for the support of the respiratory 

 irocess; and it can only be a very limited 

 mowledge of the vast wisdom displayed in 

 le arrangements of organized nature which 

 an look on the presence of so much soda 

 n the food and in the urine of the herbivora 

 s accidental. 



It cannot be accidental, that the life, the 

 evelopement of a plant is dependent on the 

 resence of the alkalies which it extracts 

 rom the soil. This plant serves as food to 

 n extensive class of animals, and in these 

 nimals the vital process is again most 

 bsely connected with the presence of these 

 Ikalies. We find the alkalies in the bile, 

 nd their presence in the animal body is the 

 ndispensable condition for the production 

 f the first food of the young animal; f( 



