METABOLISM AND THE DISTRIBUTION OF MATERIAL 245 



tion for several hours and the dilution is then undertaken, the 

 hemolysis will occur only when the cane sugar concentration reaches 

 2 per cent. Sufficient time has thus been given for salts to leave 

 the blood corpuscles and enter the cane sugar as was shown by A. 

 GURBER. 



Experiments of JAQUES LoEB* 4 upon the parthenogenesis of sea 

 urchin's eggs are in accord with this. If the eggs are placed for a 

 short time in hypertonic salt solution and then returned to sea 

 water (which corresponds with their normal osmotic pressure) seg- 

 mentation takes place. J. LoEB* 4 found that a cane sugar solution 

 acts like a hypertonic salt solution even if, as regards concentration, 

 it be isotonic with the eggs. J. LOEB explains the action by saying 

 that the egg pellicle is permeable for sugar and salts, and that the 

 salts diffuse out more rapidly than the cane sugar diffuses in, so that 

 the outer fluid becomes hypertonic. We must, moreover, recall that 

 substances exist which to a certain extent close the pathways auto- 

 matically, as for instance the SO 4 ion, whereas others, especially urea, 

 open a passage, not only for themselves but for other substances 

 (see p. 55). The permeability of red blood corpuscles and muscles 

 for urea is then no longer surprising, any more than the changes in 

 permeability (observed by M. FLURI* and R. MEURER*) in the 

 plasma pellicle of plants under the influence of certain salts. 



This may be accomplished not only by chemical agencies, but 

 purely physical factors may have an influence. It might be ex- 

 pected a priori from change in temperature; the influence of light is 

 surprising, as experiments of W. W. LEPESCHKIN and by A. TRONDLE 

 have shown. The latter's experiments indicate that plant cells 

 (foliage) are more permeable, not only for NaCl but even for glucose, 

 in a bright light than in the dark. 



One of the most remarkable and still unexplained phenomena is 

 that when death occurs, the permeability of the cell membrane 

 changes into that of an ordinary membrane which retains only col- 

 loids. 



Assimilation and Dissimilation. 



After a crystalloid foodstuff has entered the organism, it is the 

 organism's most important task to retain it for use; this is ac- 

 complished by changing it into a colloid, inasmuch as complicated 

 combinations are formed from more or less simply constructed crys- 

 talloids. From the CO 2 , which enters the leaf, starch is formed 

 under the influence of chlorophyl granules and daylight; and from 

 nitrates which have entered through the roots, with the assistance 

 of carbohydrates, proteins develop. In the animal organism, the 



