Amebic Dysentery 695 



loose the miscellaneous bacteria and come to contain the one 

 variety planted with them, or if several have been used in 

 drawing different circles, that one which they prefer to feed 

 upon. By transplanting the amebas from plate to plate with 

 suitable symbiotic bacteria for them to feed upon, the cul- 

 tures may be kept growing almost indefinitely. 



Anna Williams* has been able to grow ameba in pure 

 culture without symbiotic bacteria, either dead or alive, by 

 smearing the surface of a freshly prepared agar-agar plate 

 with a fragment of freshly removed rabbit's or guinea-pig's 

 brain, kidney, or liver, held in a pair of forceps. The 

 ameba gladly take up and live upon the cells left behind 

 upon the surface of the agar. 



Vital Resistance. The free amebas in the intestinal dis- 

 charges are easily destroyed by dilute germicides and by 

 drying. Encysted amebas are, however, more difficult to 

 kill. They resist drying well and also resist the penetra- 

 tion of germicides. Direct sunlight inhibits the activities 

 of the organisms, but does not kill them. Losch was the 

 first to observe that quinin was destructive to intestinal 

 amebas, and his observations have been reviewed by many 

 others. Musgrave and Clegg found that active cultures of 

 one ameba were killed in ten minutes by a i : 2500 solution 

 of quinin hydrochlorate. The exposed organisms quickly 

 encysted themselves, and in from five to eight minutes many 

 of them had broken up and disappeared. After ten minutes 

 all were dead. Cultures of another ameba similarly treated 

 gave a scanty growth after ten minutes. 



Exposure to i : 1000 solution of formalin did not kill en- 

 cysted amebas in twenty-four hours. Acetozone did not kill 

 amebas in i : 1000 dilutions. If, however, the acetozone was 

 made i per cent, acid to phenolphthalein the amebas were all 

 killed by i : 5000 solutions in ten minutes. 



Metabolic Products. It seems as though Entamoeba his- 

 tolytica must produce some metabolic product that exerts an 

 enzymic action upon the human tissues and thus account for 

 the destructive nature of the lesions. This has not, however, 

 been demonstrated as yet. 



Pathogenesis. Schaudinn was the first to prove the patho- 

 genic action of the organism. He inspissated the evacuations 

 of a case suffering from dysentery, so that it contained con- 

 siderable numbers of encysted amebas. When this was fed 

 ! "Journal of Medical Research," xxv, No. 2, Dec.. 1911, p. 263. 



