NOVEMBEB 3, 1911] 



SCIENCE 



587. 



isolated and uninjured for a relatively 

 long time. Another advantage offered by 

 the blood corpuscles is that the influence of 

 diverse agents on their volume and form 

 and likeness on their chemical and physico- 

 chemical composition, can be studied with 

 much exactness. Again it is possible, after 

 causing moderate disturbances in the 

 physiological equilibrium, to observe very 

 accurately the exchange of particles be- 

 tween the blood corpuscles and their nat- 

 ural medium, the blood plasma. Further- 

 more, an excellent object is given in the 

 white blood corpuscles and particularly in 

 the phagocytes for the study of the effect 

 of such disturbances on life. 



To these researches belongs among others 

 the study of permeability of different kinds 

 of cells. This study was begun in 1889 as 

 one of the results of the theory of isotonic 

 coefficients. It was found that the blood 

 corpuscles, despite the fact that their vol- 

 ume remains unchanged in an isotonic 

 salt solution, are permeable to chlorine, if 

 kept in the solution for a sufficiently long 

 time. It is hardly necessary to point out 

 how important the problem of permeabil- 

 ity is. The permeability enables the cell 

 to admit some substances into its interior 

 and to refuse admittance to others. In this 

 way the troublesome hypothesis of " con- 

 scious selection " of cells between certain 

 substances is replaced by a simple fact of 

 physics. To the pharmacologist this means 

 that remedial agents have to be in a form 

 which would make it easy for them to pene- 

 trate the interior of the cell body. 



It may well be said that so long as phys- 

 ical and physico-chemical methods are em- 

 ployed in the study of the processes going 

 on in living cells, the problem of permea- 

 bility will play an important role in physi- 

 ology as well as in pathology and in 

 pharmacology. 



Of course it must be expected, and many 



facts have already proved it, that owing to 

 the high division of labor peculiar to the 

 cells of our organism, the permeability to 

 the same substance will be different with 

 the different kinds of cells. So it is, for in- 

 stance, a well known fact that the epithe- 

 lium of the intestine is permeable to many 

 substances, to which the epithelium of the 

 urinary bladder is impermeable. 



Another important discovery which we 

 owe to physico-chemical researches was 

 made in studying the formation and re- 

 sorption of lymph. Attention was called 

 here to a driving force which must he ac- 

 curately gauged and which is based on the 

 fact that a movement of water takes place 

 from a place of low osmotic pressure to near- 

 by places where this pressure is somewhat 

 higher. This driving force is rather com- 

 mon, however, and is for instance always 

 found to play a very important role when- 

 ever a large protein-molecule breaks up 

 into smaller molecules. 



Likewise it is the same driving force 

 which, as Starling has shown, owing to the 

 osmotic pressure of the albumen, is so im- 

 portant in connection with the resorption 

 of fluids in serous cavities. 



Of course, in the instances dealt with, 

 the differences in osmotic pressure are 

 low; they correspond to only a few thou- 

 sandths of a degree of the lowering of the 

 freezing point. However, it would be a 

 mistake to think that this difference in the 

 hydrostatic pressure is without influence 

 to the organism. It must not be forgotten 

 that one thousandth of a degree of the 

 lowering of the freezing point would suffice 

 to bring about a driving force of more 

 than 0.1 m. of water pressure and that this 

 pressure does not differ much from the one 

 causing the flow of blood in the capillaries. 



These modern researches were of not less 

 importance, for the development of a new 

 branch of science, namely that of electro- 



