CHEMICAL COMPOSITION OF THOSE SUBSTANCES COMPARED. 107 



The Course of Lectures on Vegetable Chemistry was suc- 

 ceeded by a similar course on the Chemistry of Animal Life, 

 in which some of the most important parts of that branch of 

 knowledge were familiarly explained, in the following order. 

 The general nature of the organs of deglutition and digestion, 

 especially in man, was described, drawings or prints of those 

 organs being exhibited in illustration, and the latter process, 

 as well as those of chylificatiori and sanguification, embracing 

 the entire operation of the conversion of food into blood, was 

 explained. The chemical composition of animal substances 

 was next noticed, and illustrated by a comparison of the re- 

 sults of the destructive distillation of vegetable and of animal 

 matter, that of the latter being performed during the Lecture, 

 and its results examined ; Gelatine, in the form of isinglass, 

 being the animal substance selected for the experiment. This 

 naturally led to the chemical history of Ammonia, as the 

 most important and characteristic result of the destructive 

 distillation of animal matter ; and since Vegetable bodies, it 

 had been shown, might be regarded, in general, as being, es- 

 sentially, compounds of carbon and water ; so Animal sub- 

 stances, the ultimate elements of which are carbon, oxygen, 

 hydrogen, and azote, (the hydrogen being always contained in 

 them in appropriate quantity to form water with the oxygen, 

 and ammonia with the azote,) might be regarded, it was shown, 

 as essentially consisting of carbon, water, and ammonia*. 



* The statement that the hydrogen contained in the more important 

 animal principles, (, those which are neither acid nor oleaginous,) is in such 

 proportion, as to convert their oxygen into water, and their azote into am- 

 monia, having been adopted from Gay-Lussac and Thenard, by Dr. Turner 

 and other chemists, appeared to be sanctioned by their authority ; it was 

 eminently adapted to the purposes of these lectures by its simplicity, and 

 its analogy to the statement already given of the constitution of the vege- 

 table principles, and by the readiness with which it might consequently be 

 retained in the memory : on these accounts it was made use of throughout 

 this course on Animal Chemistry. But while the statement that the vegeta- 

 ble principles which are neither acid nor oily or resinous (together with one 

 acid principle, the Acetic), contain oxygen and hydrogen in the exact pro- 

 portions for forming water, is rigorously accurate, the analogous statement, 

 as above enunciated, respecting the corresponding animal principles, cannot 

 be regarded, I think, in the present state of science, as fully established j 

 and there seems reason to believe that it will be found inapplicable to more 

 than one of the compounds which have been included in it by Gay-Lussac 

 and Thenard. Dr. Turner has prefaced the division on Animal Chemistry 

 of his " Elements " of that science, by a repetition of this statement ; but 

 out of the six analyses of the bodies to which it relates, some by Gay- 

 Lussac and Thenard, and others by Dr. Prout, which Dr. Turner has cited 

 in the subsequent pages of that division, there is only one, that of fibrine, by 

 the former chemists, which supports the statement. In four of the others 

 there is an excess of hydrogen, and in the remaining one a deficiency of that 

 principle. And although this discrepancy may be in some measure attri- 



