ACTION OF DRUGS 255 



It has long been known that ipecacuanha is a specific for amoebic 

 dysentery, but Vedder (1912) was the first to show that this action of 

 ipecacuanha depended upon the alkaloid emetine. Rogers (1913), in 

 India, was the first observer to introduce this alkaloid in the routine 

 treatment of amoebic dysentery, a course which had been previously 

 recommended by Vedder (1912). The latter observer believed that it 

 acted directly on the amoebae and poisoned them, and Rogers made 

 similar claims. It appears, however, as has been demonstrated by the 

 writer and others, that active E. histolytica, either in faeces or liver- abscess 

 pus, can be mixed with relatively strong solutions of emetine, and that 

 the amoebae will remain as perfectly active as those in control preparations. 

 Unless it is assumed that the medium in which the amoebae happen to 

 be — namely, the faecal matter or the pus — absorbs or fixes the emetine, 

 so that it never actually comes in contact with the amoebae, it must be 

 concluded that the alkaloid has no immediate toxic action on the amoebae. 

 That such an explanation of the failure of emetine to kill amoebae in 

 these experiments may have something in its favour is borne out by 

 certain tests made by Pyman and the writer (1917) on cultures of free- 

 living amoebae on agar plates. The agar was made up with varying 

 strengths of different salts of emetin, and it was found that the amoebae 

 did not grow on the medium which contained the salts, which are known 

 to be specifics for amoebic dysentery, though the bacterial growth upon 

 which the amoebae feed was little altered in character. Furthermore, it 

 has been shown by Brown (1922) that if the emetine solution which is to 

 be introduced into the agar is first mixed with pus for a few minutes, the 

 liquid portion separated by centrifugation has lost its power of arresting 

 growth of amoebae on the plate. It would seem that in this experiment 

 the dead cells and debris in the pus had absorbed the emetine from the 

 solution, so that there may be some reason for suspecting that when 

 material such as faeces or pus containing E. histolytica is mixed with 

 solutions of emetine, the failure of the drug to kill the amoebae may be due, 

 in part at least, to its absorption by the dead material. It has also to be 

 remembered that even if emetine has no direct action on E. histolytica 

 exposed to it for a comparatively short time, it may still have such an 

 action over a longer period in preventing growth and multiplication.' 

 It should be possible to test this point on cultures of E. histolytica. 



Dale and Dobell (1917) investigated the action of emetine on experi- 

 mentally infected cats, and came to the conclusion that the drug only in- 

 directly kills £'. histolytica by acting primarily on the host. In the case of 

 cats they stated that it neither acts as a prophylactic when given before 

 infection is attempted, nor as a curative agent after E. histolytica has estab- 

 lished itself in the large intestine. Mayer (1919) had similar experiences, 



