ELEMENTS OF FOOD. 97 



power of formiHg, from the constituents of its blood, 

 the substance of its membranes and cellular tissue, 

 of the nerves and brain, of the organic part of carti- 

 lages and bones. But the blood must be supplied 

 to it ready formed in every thing but its form — that 

 is, in its chemical composition. If this be not done, 

 a period is rapidly put to the formation of blood, 

 and consequently to life. 



This consideration enables us easily to explain 

 how it happens that the tissues yielding gelatine or 

 chondrine, as, for example, the gelatine of skin or of 

 bones, are not adapted for the support of the vital 

 process ; for their composition is different from that 

 of fibrine or albumen. It is obvious that this means 

 nothing more than that those parts of the animal 

 organism which form the blood do not possess the 

 power of effecting a transformation in the arrange- 

 ment of the elements of gelatine, or of those tissues 

 which contain it. The gelatinous tissues, the gela- 

 tine of the bones, the membranes, the cells, and the 

 skin, suffer, in the animal body, under the influence 

 of oxygen and moisture, a progressive alteration ; a 

 part of these tissues is separated, and must be re- 

 stored from the blood ; but this alteration and re- 

 storation is obviouslv confined within very narrow 

 limits. 



While, in the body of a starving or sick individual, 

 the fat disappears, and the muscular tissue takes 

 once more the form of blood, we find that the ten- 

 dons and membranes retain their natural condition ; 



H * 



