CHAP, v.] NUTRITION. 427 



the protoplasm; when formed, however, it appears to be dis- 

 charged from the cell in a more or less mechanical manner, as the 

 needs of the economy demand. And this view is supported by 

 the fact that protoplasm, wherever occurring, both during life and 

 after death (when it could not possibly be supplied with fat from 

 without), is subject to fatty degeneration, in which the fat evi- 

 dently arises, in large part at least, from the breaking up of 

 proteid compounds. 



On the other hand, we have traced the fats taken as food, and 

 found that they pass with comparatively little change from the 

 alimentary canal, chiefly through the intermediate passage of the 

 lacteals, into the blood. We might infer from this that an excess 

 of fat thus entering the blood would naturally be simply stored up 

 in the available adipose tissue, without any further change, the 

 connective-tissue corpuscles eating the fat brought to them after 

 the fashion of an amoeba but not digesting it, simply keeping it 

 in store till it was wanted elsewhere. 



Which of these views is the true one, or how far are both 

 these operations carried on in the animal body? In the first 

 place, it is evident that in an animal fattened on ordinary fattening 

 food, only a small fraction of the fat stored up in the body can 

 possibly come direct from the fat of the food. Long ago, in 

 opposition to the views of Dumas and his school, who taught that 

 all construction of organic material, that all actual manufacture of 

 protoplasm or even of its organic constituents, was confined to 

 vegetables and unknown in animals, Liebig shewed that the butter 

 present in the milk of a cow was much greater than could be 

 accounted for by the scanty fat present in the grass or other fodder 

 she consumed. He also urged, as an argument in the same 

 direction, that the wax produced by bees is out of all proportion to 

 the fat contained in their food, consisting as this does chiefly of 

 sugar. And Lawes and Gilbert have shewn by direct analysis that 

 for every 100 parts of fat in the food of a fattening pig, 472 parts 

 were stored up as fat during the fattening period. It is clear that 

 fat is formed in the body out of something which is not fat. 



There are two possible sources of this manufactured fat. In 

 treating of digestion (p. 298), we referred to the possibility of 

 digested carbohydrates becoming by fermentation converted into 

 butyric acid; and we may imagine that when a member of 

 the fatty acid series had thus been formed, higher and more 

 complex members of the same series might be obtained out of it. 

 There can be no doubt indeed that a carbohydrate diet is most 

 efficacious in producing an accumulation of fat in the body : sugar 

 or starch, in some form or other, is always a large constituent of 

 ordinary fattening foods. 



Another source of fat is to be found in the proteids. We have 

 seen that the urea of the urine practically represents the whole of 

 the nitrogen which passes through the body. Now in any given 



