EXCHANGE OF MATERIAL. 449 



exchange of material in the various organs during starvation. For 

 instance, the nervous system only shows a small loss of weight as 

 compared to the other organs, but from this it must not be con- 

 cluded that the exchange of material in this system of organs is not 

 active. The condition may be quite different ; for one organ may 

 derive its nutriment during starvation from some other organ and 

 exist at its expense. A positive conclusion cannot be drawn in 

 regard to the activity of the exchange of material in an organ from 

 the loss of weight of that organ in starvation. 



II. Exchange of Material with Inadequate Nutrition. 



The food may be quantitatively insufficient and the final result 

 is absolute inanition. The food may also be qualitatively insuffi- 

 cient, or as we say, inadequate. This occurs when any of the 

 necessary nutritive bodies are absent in the food, while the others 

 occur in sufficient or perhaps indeed in excessive amounts. 



Lack of water in the food. The quantity of water in the 

 organism is greatest during foetal life, and then decreases with 

 increasing age (v. BEZOLD). Naturally, the amount differs in 

 various organs. Enamel, being almost free, contains only 2 p. m. 

 water, the teeth about 100 p. m., the fatty tissues and bones 

 60-120-150 p. m. The cartilage with 540-740 p. m. is somewhat 

 richer in water, while the muscles, blood, and glands with 750 to 

 more than 800 p. m. are still richer. The quantity of water is even 

 greater in the animal fluids (see preceding chapter), and the grown 

 body contains in all about 600 p. m. water (BISCHOFF). If we bear 

 in mind that two thirds of the animal organism consists of water ; 

 that water is of the very greatest importance in the normal, phy- 

 sical composition of the tissues ; moreover that all flow of juices, 

 all exchange of substance, all supply of nutrition, all increase or 

 destruction, and all discharge of the products of destruction are 

 dependent upon the presence of water; besides this, that by its 

 evaporation it is an important regulator of the temperature of the 

 body, we perceive that water must be necessary for life. If the 

 loss of water be not replaced by fresh supplies sooner or later, 

 the organism succumbs. 



Lack of mineral substances in the food. We are chiefly in- 



