22,1 Sellards and Leiva: Amoebic Dysentery 19 



action which it exhibited in several instances when administered 

 therapeutically to infected kittens. 



These experiments furnish no direct evidence concerning the 

 mechanism of the action of emetine in amoebic dysentery. In 

 the recovery of patients, we must consider both the resistance 

 of the host to amoebae and the effect of emetine. Clinical 

 evidence is very convincing that the normal individual exhibits 

 considerable natural resistance to Entamoeba histolytica, lead- 

 ing ordinarily to spontaneous remission of symptoms even in 

 untreated patients. Emetine is not only moderately toxic for 

 amoebae in vitro, but is also distinctly toxic for mammals. It 

 does not seem likely to us that E. histolytica in its host can 

 entirely escape this toxic action. The maximal therapeutic doses 

 of emetine are relatively small, but they are cumulative in their 

 effect. Until there is experimental evidence to the contrary, we 

 prefer to adhere to the following working basis : That recovery 

 from amoebic dysentery in man and in lower animals results 

 from the combined action of the natural resistance of the host 

 and a moderate action of emetine on the amoebae. The sum- 

 mation of these two factors is necessary for radical cure. A 

 lowering of either allows the disease to progress. Minimal 

 doses of emetine do not modify the course of the infection. The 

 effect of feeble natural resistance of the host is beautifully 

 illustrated by the fulminating infections seen in young kittens. 



A comparison of the effective dosage of emetine in man and 

 in experimental animals is difficult, on account of the severity 

 of the artificial infection. Moreover, patients are treated by 

 small doses over a period of many days or weeks, whereas the 

 animals must be treated intensively for a short period. The 

 following outline (Table 3) shows the relation between the 

 ordinary therapeutic dose used in man and the quantities that 

 we have employed. These have been arranged to show both 

 the initial dose required to check the symptoms and the total 

 quantity for eradicating an infection. The latter is extremely 

 variable in man, and the figures given represent optimal results. . 

 Table 3. — Showing the amounts of emetine hydrochloride used in the treat- 

 ment of amoebic dysentery in man and in cats; milligrams per kilo- 

 gram of body weight. 



