108 LECTURES ON ANIMAL CHEMISTRY. 



The nature of ammonia was illustrated by reference to the 

 various preparations of that substance and its salts, many of 

 which, from the circumstance of their being obtained, at a 

 former period, chiefly by the destructive distillation of the 

 horns of Deer, (as they now are by that of the horns, hoofs, and 

 refuse skin of animals in general,) have been called salts of 

 Hartshorn, spirits of hartshorn, &c. ; and including common 

 smelling saltS)OY the sesqui-carbonate of ammonia of Chemists. 

 The physiological nature and the chemical composition of 

 the blood were next described, the opportunity being taken 

 of explaining the history of Albumen, as the most important 

 element of the blood, illustrated by experiments on the white 

 of eggs, which consists of that principle nearly in a state of 

 purity. The nature of the blood having thus been explained, 

 the phaenomena of its circulation through the body were de- 

 tailed, accompanied by graphic illustrations of the organs 

 concerned in that process. After the performance of a 

 few experiments (similar to those made at the beginning of 

 the Course on the Supporters and Combustibles, as described 

 at p. 85) showing the existence of two distinct species of air 

 in that which we breathe ; and that one only of these the 

 Oxygen is the supporter of life ; and after some preliminary 

 information had been imparted on the nature of carbonic acid 

 gas, also experimentally demonstrated, the alteration induced 

 in atmospheric air, by respiration consisting in the exchange 

 of a portion of its oxygen for an equal bulk of carbonic acid, 

 was experimentally shown. With this subject the Course 

 was concluded, in which the composition, properties, and 

 functions of the blood, as the great agent in building-up the 

 animal frame, had thus been examined, together with the 

 provision for preserving it in a fit state for the requirements 

 of the body, (and also for the completion of the process by 

 which chyle, or digested food, becomes blood,) by the action of 

 the atmosphere. 



During the entire period of the delivery of these Lectures, 

 I was required, by the arrangements adopted for the tuition 

 of the various classes at Bruce Castle, actually to teach 



butable to errors in the analyses, as minute accuracy in the analysis of 

 organic bodies is so difficult of attainment, especially, perhaps, of such 

 as contain azote in addition to hydrogen, yet the deviation from the rule, of 

 albumen and urea, as evinced by Dr. Prout's analyses of those bodies, can 

 scarcely, I conceive, be ascribed to that cause. Dr. Prout's forthcoming re- 

 searches on the animal principles, in continuation of those already pub- 

 lished by him on the composition of the simple alimentary substances, will 

 probably remove the obscurity in which this subject is at present involved. 



