116 LECTURE VI. 



sodium chloride solution, and adding only one drop of serum to this, 

 after having previously shown that cobra poison alone had not caused 

 hemolysis. S. Flexner and H. Noguchi, who first observed this fact, and 

 noticed it also with other poisons (tetanustoxin, solanin, saponin, etc.), 

 rightly concluded that some substance was undoubtedly present in serum, 

 which made it possible for the cobra poison to act on the hemoglobin of 

 the corpuscles. P. Kyes then succeeded in showing that lecithin could be 

 substituted in place of serum. Minute traces are sufficient to cause hemo- 

 lysis. Lecithin alone, when used in small quantities, does not act hemolyti- 

 cally, but lecithin and the cobra poison together do so. This is not the 

 place to dwell upon this interesting biological phenomenon and its expla- 

 nation. We must content ourselves with the knowledge that lecithin 

 possesses the capacity of accelerating the activity of poisons. Many 

 interesting questions are suggested by this fact. It is entirely possible 

 that lecithin also acts as an accelerator in the animal cells, and even on 

 the intracellular ferments. As a result of recent investigations we are 

 forced to conclude that the ferments as a whole are not released from the 

 cells in their active form, but that they require the influence of a second 

 substance to develop their activity. With such an hypothesis we can 

 easily explain the action of ferments in the cells. 



To lecithin is ascribed a large influence in the construction of the cell- 

 walls, and also in the resorption of the cells. What was said concerning 

 the fat contents of cells is also applicable to this case. Lecithins act as 

 solvents. 



There is another substance, which, although not at all related to lecithin 

 chemically, is like lecithin indispensable to all cells. This is cholesterol. 

 Its various modifications are widely distributed in the vegetable kingdom. 

 Vegetable cholesterins are designated phytosterols. In the animal organ- 

 ism it is found in all cells, in the blood, lymph, etc. It occurs in excep- 

 tionally large amounts in the brain and nerve tissues. In the gall bladder 

 it often gives rise to the formation of calculi, although this is almost 

 always a secondary effect, and a result of disease of the bladder (catarrh, etc.) 

 It forms white, fatty-feeling crystals with a pearly luster. It is absolutely 

 insoluble in water. Sometimes cholesterol occurs in the free condition, as 

 in the blood corpuscles; 1 then again it forms ester combinations. For 

 instance, it is united with fatty acids 2 in the blood. Schulze isolated an 

 isomer of cholesterin from wool fat, called isocholesterol. 3 



The way cholesterol is formed is still unknown to us. We do not at 

 present know its constitution. All that we knew up to within a short 



1 E. Abderhalden: loc. cit. 



2 K. Hiirthle: Z. physiol. Chem. 21, 331 (1895-96). E. Hepner: Pfliiger's Arch. 

 1898, 73. 



3 Ber. 5, 1075 (1872), and 6, 251 (1873). 



