370 PROTOPLASMIC ACTION AND NERVOUS ACTION 



Nerve is affected similarly; and the characteristic 

 pharmacological effects produced by this group of salts, 

 e.g., their cathartic action (which apparently depends 

 upon a heightening of contact-irritability in the intestinal 

 tract), are probably referable to conditions of a similar 

 kind. There is much evidence that many forms of 

 pharmacological action are due to changes in the physical 

 consistency, permeabihty, chemical alterabihty, or other 

 properties of the protoplasmic surface-films. 



It is important to note the relation of sensitizations 

 of the class described — which consist in a general heighten- 

 ing of irritability toward non-specific chemical or other 

 stimulating conditions — to the class of specific sensitiza- 

 tions, of which anaphylaxis is the most striking example. 

 The general features of this phenomenon are well 

 known. During the early stages of the process of 

 immunization, following the introduction of a foreign 

 protein into the circulation, the cells of the mammalian 

 organism become highly sensitive to the introduction of 

 further protein of the same kind, and in certain animals, 

 notably the guinea-pig, the most conspicuous effect of 

 the second injection is seen in the smooth muscle cells, 

 especially those of the respiratory tract; these contract 

 firmly and persistently and occlude the bronchioles, 

 with death by asphyxiation as a consequence. This 

 contraction-producing effect is almost certainly depend- 

 ent on a specific antigen-anti-body reaction occurring 

 in the surface layer of the muscle cells. The promptitude 

 with which it follows injection of even a small quantity 

 of the foreign protein indicates this, since the latent 

 period seems insufficient for penetration into the cell 

 interior; such a conclusion receives further support 



