314 DR ALISON'S OBSERVATIONS ON 



in vegetables or animals, which are distinctly at variance with the ordinary laws 

 of chemistry, and which we must therefore ascribe to vital affinities ? 



It is evident that what, in physiological language, is commonly called Assimi- 

 lation, includes two distinct actions, both, in many cases, as I believe, strictly vital ; 

 first, the mere selection and attraction of a part of a compound fluid, to be added 

 to a living body ; and, secondly, the transformation of the elements of two or more 

 compounds, so as to form a new compound, similar to one already existing in the 

 living body wherein this change occurs. If Dumas's view of the subject were to 

 be adopted, we should say that animals can exert only the first of these powers, 

 the simple selection and attraction of one of the ingredients of a compound fluid 

 by each organ or texture, without any power of transformation, or formation of new 

 compounds ; and accordingly, he says that " it is in plants that the true labora- 

 tory of organic chemistry resides." 



But if we state the proposition thus generally, we may state various facts 

 to shew, that it is incorrect. It is quite certain, as already stated, that oil or fat 

 may he formed in animal bodies, by a new arrangement of the elements of starch, 

 attended by an evolution of much of its oxygen, and of part of its carbon and hy- 

 drogen, effected by the aid of the oxygen of the air ; and the influence (already 

 noticed) of exercise, i. e., of an increased application of oxygen, on this change, 

 shews distinctly that the recent ingesta are liable to two influences in a living 

 animal, one of which is an action of oxidation or combustion, throwing off" water 

 and carbonic acid, but the other is strictly an action of reduction, by which a 

 quantity of oxygen is separated from its combinations in an organic compound, 

 while a fresh compoimd, constituting part of the animal frame, is formed. And 

 the fat of the animal body, which may be thus formed, is not to be considered as 

 a merely unorganized appendage to the textures. It appears from some of Liebig's 

 observations, that the muscular flesh of aU animals, after being cleared of all visible 

 fat, still retains a considerable and variable quantity in its substance ; and we 

 know that in two of the most important textures of the body, nervous matter 

 and bone, fat is an essential ingredient. 



In like manner, the formation of the essential ingredient Gelatin in the ani- 

 mal body is the result of a new arrangement of elements, attended with evolu- 

 tion of carbon and hydrogen, by the aid of the oxygen of the air, but probably 

 not with absorption of oxygen. 



In the case of Inflammation, we see distinctly that, in connection with an in- 

 creased action of nutrition or deposition of plastic lymph, there is a transforma- 

 tion of portions of the blood to form the compound, very similar to gelatin, termed, 

 by MuLDEit, tlie Tritoxide of Protein, which is found there in very unusual quan- 

 tity ; and in other morbid actions, in certain chronic malignant diseases, we see 

 compounds, altogether foreign to the natural organization, formed and even ra- 

 pidly extended ; the formation of which is certainly neither a simply chemical act 



