110 life's beginning on the earth 



excreted through the natural channels; the blood is inces- 

 santly driven around; body fluid passes into the blood or 

 vice versa; the oceanic salt solution in our body is in con- 

 stant motion. Before we can hope to understand the mode 

 of working of the vital organs of our body we have to know 

 the laws which regulate the water exchange in it. 



The most casual survey shows that the role which water 

 plays in the body economy is very complicated. The 

 following example may serve to illustrate this point. In 

 most cases of starvation or wasting diseases, such as cancer 

 or tuberculosis, large amounts of water are lost along with 

 the solid body building material. In other cases, of sim- 

 ilar ailments however, a retention and a piling up of large 

 amounts of water may occur (Fig. 31). This is known as 

 edema or anasarca. Cases of hunger edema are usual in 

 the great famines which at times visit Russia, China, or 

 India. While most of the unfortunate victims of starvation 

 resemble walking skeletons, some of them develop enor- 

 mously distended arms, legs and abdomens. Why does the 

 water escape from the body in one case, while in another, 

 water is piled up? 



This question can be answered if we understand the com- 

 plicated mechanism through which water may enter or 

 leave the organism. Nothing is gained by inventing new- 

 descriptive terms to explain this mechanism; instead we 

 should start with simple experiments on non-living models. 

 We can construct what we may call an artificial cell, a con- 

 trivance capable of attracting or giving off water under con- 

 ditions similar to those existing in living tissues. 



Here is the method of preparing such an artificial cell: 

 A solution of gelatin is made and a drop taken out of this 

 solution with a glass rod. The drop remains hanging at the 

 end of the rod, and is exposed to the air for several hours. 

 It is then dipped into a 5% solution of tannic acid. In 

 about ten minutes a thin iridescenl solid film forms at the 



