AUGUST 19, 1921 alsberg: physiological chemistry 325 



related to their effects upon colloids, especially proteins ;^^ but here 

 again the power of kations to precipitate proteins and of anions to 

 produce the reverse effect is, so far as our knowledge at present goes, 

 an intrinsic property. Since it is, speculation upon these phenomena 

 is rather fruitless till the physicists have gone a great deal further. I 

 shall deal tonight therefore in the main with substances more complex 

 than the simple elements. 



There are in the main three general ways in which a substance may 

 affect a cell: 



The substance may attack the surface of the cell. 



The substance may affect the cell indirectly without entering it. 



The substance may affect the cell in the course of entering, or after 

 entrance into the cell. 



Many substances destroy the surface layer of a cell by precipitating 

 or coagulating it. This is the effect of many astringents, such as the 

 salts of many heavy metals, ferric chloride for example, when in 

 sufficient concentration. Other substances dissolve some of the 

 constituents of the surface layer as, for example, ether when in sufficient 

 concentration.^^ Other substances combine with some component of 

 the surface layer. This may be the action of saponins. ^^ 



Substances which neither enter cells nor attack the cell surface act 

 chiefly by affecting the concentrations within the cell. They either 

 withdraw water from the cell so that it tends to shrivel and become 

 desiccated, or they cause water to penetrate into the cell so that it 

 swells. These processes are called plasmolysis because they may, if 

 carried to extremes, cause the protoplasm to disintegrate. Those 

 among you who are botanists or physiologists know that this phenom- 

 enon may be studied by observing the behavior of suitable plant 

 cells or red blood corpuscles when placed in solutions of the substances 

 to be tested. In many plant tissues the protoplasm forms a layer 

 lining a rigid cellulose wall. It is really a sac enclosing a relatively 

 large space filled with sap. When such a cell shrinks or is plasmolyzed 

 the protoplasm withdraws from the cellulosic cell wall and this can be 

 seen very easily under the microscope. In the case of red blood 

 corpuscles, these become crenated, that is, they shrink and take on the 



11 Bayliss, op. cit., p. 35. 



12 L. Hermaxn. Ueber die Wirkungsweise einer Cruppe von Giften. Arch. Anat. Physiol, 

 u. Wiss. Aled. 1866: 27. 



1' H. E. Woodward and C. L. Alsberg. A comparison of the effect of certain saponins 

 on the surface tension of water with their hemolytic power. Journ. Pharm. Exp. Therap. 

 16: 237. 1920. 



