212 DIGESTIVE SYSTEM. 



property of forming wax, which is a fatty substance. The 

 possibility of an animal organism making any fatty substance 

 used to be denied by many chemists and physiologists. 



The animal and vegetable kingdoms also contain sub- 

 Btances which resist the action of the digestive juices, and 

 consequently pass through the intestinal canal only to reap- 

 pear in the excrementitious products, separated from the 

 alimentary principles accompanying them. These are, on 

 the one hand, elastic and connective tissue, the digestion of 

 which is very difficult and even impossible to some persons ; 

 and, on the other, numerous vegetable elements the most 

 common form of which is the cellular or ligneous, forming 

 the skeleton of most vegetables, the envelope of certain 

 seeds, etc. 



There is, finally, a peculiar class of substances, which must 

 be considered as aliments, though they undergo little or no 

 change in passing through the system and the interior of 

 the tissues ; they appear to produce the effect of diminishing 

 combustion, or rather of rendering it more efficacious : in 

 short, they promote the transformation of heat into force, 

 and render the true alimentary substances previously in- 

 gested, more useful. Whence the name of reserve or eco- 

 nomical aliments, bearers of force (dynamophorous). This 

 singular class of substances which are not alimentary, and 

 yet are aids to alimentation, has been the subject of numerous 

 investigations, showing their number and the mode of action 

 peculiar to each. Alcohol stands at the head of this class : 

 according to many physiologists alcohol is burned in the sys- 

 tem, serving thus to produce heat immediately (Liebig, Hepp, 

 Hirtz, Schulinus) ; but recent investigations of Lallemand and 

 Pen-in show that if alcohol be received into the system it merely 

 passes through it, and is always found again, as in the blood 

 and tissues, especially the nervous tissue, in which it appears 

 to take up its abode for some time : in short, it is not con- 

 sumed, and its presence as an alimentary substitute only 

 serves, by economizing combustion, to increase its utility. 

 We can understand thus, that alcoholic drinks may be indis- 

 pensable, in some degree, to a man who is obliged to perform 

 severe labor, with insufficient nourishment ; as to the fatal 

 excess which so often succeeds a moderate use of these 

 drinks, physiology shows us that our efforts should be directed 

 less against this, than against the conditions which make the 

 use of alcohol an imperious and fatal necessity for the work- 

 ing-man (Moleschott). 



