48 ANIMAL CHEMISTRY LECTURE III. 



molecules to their appropriate positions in certain definite series 

 and groups ; and had every reason to believe that with increasing 

 knowledge we should be able to make the assignment in every 

 instance. 



(45.) Moreover, in my first lecture I pointed out to you that 

 organic chemistry had a statical aspect which related to the com- 

 position of bodies, and a dynamical aspect which related to their 

 changes of composition. But in all that I have hitherto ob- 

 served I have had regard principally to the statical aspect of 

 the question. I have glanced, indeed, at the mutual metamor- 

 phosis by oxidation and deoxidation of compounds belonging to 

 the same natural group ; and have referred more fully to the 

 combination of their several residues with one another in forming 

 complex tissue products, and to the separation of the completed 

 residues from one another in the breaking up of these products ; 

 but I have not yet considered the mode in which the primary con- 

 stituent molecules are themselves produced, or yet the mode in 

 which, when once produced, it is possible for us to destroy them, 

 and to these points I will now direct your attention. 



(46.) If we treat the more complex members of our series of 

 fatty acids, for instance, with powerful oxidising agents, we 

 obtain bodies in which the number of the constituent atoms of 

 hydrogen and carbon becomes progressively less and less, until 

 we arrive at bodies containing only two, and finally at bodies 

 containing only one carbon-atom. In some cases these succes- 

 sive oxidation products are found to contain the same number of 

 atoms of oxygen as the bodies from which they were produced, 

 though in the majority of instances they contain a greater 

 number, and consequently belong to more oxygenised series. 

 But whether they contain the same or a greater number of 

 oxygen atoms, we find the number of their atoms of carbon and 

 hydrogen become gradually less and less, their molecules pertain- 

 ing to simpler and simpler groupings. For example, the follow- 

 ing intermediate compounds, among many others, have been 

 successively obtained by oxidising stearic acid CigH^Oa, with 

 nitric acid of moderate strength : 



