216 COLLOIDS IN BIOLOGY AND MEDICINE 



higher plants, the spreading of the seed pods upon drying leads to 

 movements which serve to distribute the seeds. Best known is the 

 " blooming," or the swelling of the " Jericho-rose." Higher animals on 

 the other hand are very sensitive to losses of water: frogs, according 

 to KUNDE, may withstand a gradual loss of water up to 30 per cent, 

 but, if they are rapidly dried, they perish when the loss is only 18 

 per cent. In the latter case, there is evidently no time for an equali- 

 zation in the distribution of the water. Thirsting human beings also 

 show great losses of water, though of course, there are no data as to 

 the lethal point. A. DURIG informs me that, after a forced march 

 in hot weather, he lost 5 kg. of water. The investigations of N. 

 ZUNTZ and SCHUMBERG on marching soldiers, as well as those of N. 

 ZUNTZ on mountain climbers, showed that exercising men lost water. 

 Roughly measured, the water ingested after forced marches does 

 not replace the water lost. We may say here, anticipating some- 

 what, what animal experiments of H. GERHARTZ* show, that the loss 

 of water affected primarily the musculature and then the fluids cir- 

 culating in the organs. 



Freezing (gefrieren) 1 has an effect on the organism similar to the 

 withdrawal of water. It was formerly believed that the formation of 

 ice burst the cell walls or tore the protoplasm, and the damage from 

 freezing was ascribed to these gross mechanical influences. It was 

 shown by the investigations of A. E. NAGELI, W. SACHS, H. MOLISCH, 

 and MULLER-THURGAU that these views were false, that usually 

 there was no formation of ice in the cell, but that the ice crystals 

 grew between the cells in the intercellular spaces. P. MATRUCHOT 

 and MOLLIARD* studied plant cells and found that the phenomena 

 observed in drying or plasmolysis resembled those induced by freez- 

 ing (erfrieren). H. W. FISCHER, * l as the result of exhaustive studies, 

 reached the conclusion that the damage done to animals and plants 

 by freezing them (gefrieren) was analogous to the partially irre- 

 versible changes produced in gels by glaciation. He believes that 

 the adsorption of electrolytes in particular is thus affected unfavor- 

 ably. If a solution of potato starch is frozen and then thawed out, 

 the electrolytes may entirely dissolve again but the starch has 

 become insoluble. Frozen leaves present an analogous condition in 

 that the chlorophyl is no longer retained. In this valuable work he 



1 Freezing (erfrieren) and glaciation (gefrieren) must not be confused. A plant 

 or an animal freezes if life processes cease by reason of the low temperature. 

 This temperature depends upon the nature of the organisms involved, and in 

 the case of warm-blooded individuals is usually far above zero; in the case of 

 other organisms (seeds and spores), however, it may be far below zero (200). 

 Glaciation always means ice formation. 



