SALT AND WATER IN LIFE AND GROWTH 



145 



The microscopic study of artificial structures frequently 

 reveals parallel striations of the developing branches or 

 fibers, as is distinctly seen in the vermiform structure of 

 Figure 47a. Such a stripe formation has no direct relation 

 to the expanding osmotic forces. It can best be studied by 

 a special technique developed by R. E. Liesegang in 1896. 



Fig. 56. Worm-like Structures Growing in All Directions 



(One-half natural size) 



Here is a series of photographs taken consecutively at short intervals, 

 showing how a sprouting artificial growth can develop in all directions, 

 first up, then horizontally, and finally downward; see first photograph, 

 After it had developed so far, it broke at its uppermost point and the 

 section growing down was carried upward because the solution in which it 

 grew was much heavier than the structure itself. But the growth was 

 again continued persistently downward as shown in the last of the series. 



This shows that gravity is not an indispensable factor in the development 

 of these structures. Osmotic pressure overcomes the action of gravity in a 

 striking manner. It is quite evident that in this experiment, the direction 

 in which the artificial growth develops is determined solely by osmotic 

 forces and not by gravity. 



Details of this technique and the strikingly beautiful stria- 

 tions obtained by it are given in Figure 54 with its legend. 

 (Turn back to page 143; see also Fig. 55.) 



Regularly striped structures are frequently found in 

 living tissues of plants and animals. Thus the lime salts, 

 of which the solid bones of our body are built, are laid down 

 around the blood vessels running through the bones (Haver- 

 sian canals) in regularly striated layers. Other well known 



