8 THE SCOPE OF THE NEW METHOD 



alkaloids, and a few other substances ; but a whole field 

 of investigation of the actions of substances on indi- 

 vidual cells remains to be carried out, and this is now 

 possible by this "jelly" method of in-vitro staining. 



The action of chemical substances on living cells 

 is closely associated with the diffusion of substances 

 into these cells (a subject to which a section of this 

 book will be devoted), and this diffusion is governed 

 by the "coefficient of diffusion" of the cells them- 

 selves, a phenomenon which has been so far entirely 

 studied by this in-vitro method. Up to the present, 

 however, we have only had time to ascertain the com- 

 parative rates of diffusion of substances into some of 

 the classes of human cells and into a few species of 

 bacteria. The determination of the coefficients of 

 diffusion of all the rest of the cells of the whole ani- 

 mal and vegetable kingdoms remains as a "legacy" 

 for those who will undertake the work. 



Methods will be described by which the lengths of 

 the lives of leucocytes can be measured after they 

 have been removed from the body. By this means 

 the comparative effects of different poisons on the 

 cells can be tested, and the small amount of work 

 done in this direction will be summarised. We think 

 that there are possibilities that farther investigation 

 of the actions of specific poisons, such as bacterial 

 toxins, will lead to fruitful results; in fact, one of us 

 (C. J. M.) has already shown by this method that 

 chorea and rheumatism are less closely related than 

 is generally supposed. 1 



1 British MedicalJournal, August 23, 1909. 



