IONS AND LIPOIDS 101 



salt is dissociable into ions before it reaches the cells, 

 and the protoplasm is not so permeable to the ions 

 as to the ester. There are numerous drugs having 

 an ester-like construction. Cocaine is the methyl- 

 ester of benzoyle-ecgonin ; eucaine is an ester ; the 

 orthoforms and ansesthesin are likewise esters. It 

 is the presence of the alcohol radical which renders 

 this effect possible ; and the saponification of the 

 ester by union with the lipoids of the protoplasm 

 liberates the anion and permits it to become effec- 

 tive. Cocaine is twenty times more effective as an 

 anaesthetic than benzoyle-ecgonin ; nevertheless the 

 latter is the active principle of cocaine and is disso- 

 ciated from it by union with the lipoids of the cell. 

 " Existence in the form of an ester is a sine qua non 

 of a useful local anaesthetic whose active anions 

 must enter the endings of the sensory nerves."* A 

 consideration of the subject of narcosis was made by 

 Meyer. When a substance is put into a vessel with 

 two unmixable fluids such as oil and water, the 

 amount of the substance which is dissolved in the oil 

 and in the water was found by him to bear a definite 

 proportion or relationship to each other. This ob- 

 servation led him to form a theory of narcosis which 

 was based upon the distribution of the active sub- 

 stance between the watery fluids of the tissues and 

 the fat-like constituents of the nerve cells. 



The activity of metallic ions can also be increased 

 by combination with an alcohol-radical or trans- 

 formation into an ester ; and most acute metallic 

 intoxication can be brought about in animals by 



* Pauli's "Physical Chemistry in the Service of Medicine," 

 p. 95. 



