LOESCHIA 



3^7 



These researches clearly prove that the method of infection is by 

 cysts passed in faecal matter entering the flies, and so reaching human 

 food, as direct fsecal contamination is not so likely, though, of course, 

 it may also be a method of infection. 



Further, these cysts are spread abroad by the fsecal matter of 

 human carriers — i.e., persons who have recovered from amoebic 

 dysentery, and even those who have never suffered in this manner. 

 These carriers are the human reservoir of the parasite. 



Diagnosis. — -Amoebae present in human faeces and containing red 

 blood-corpuscles are, as a rule, L. histolytica. Amoebae without 

 red corpuscles require differentiation by the cysts, which must be 

 sought during several days. Quadrinucleate cysts belong to 

 L. histolytica, others are doubtful or definitely negative. 



Cultivation. — Since the days of Auerbach in 1856 attempts have 

 been made to cultivate pathogenic amoebae in pure or contaminated 

 cultures. With regard to L. histolytica all such attempts were 

 failures until Cutler apparently succeeded, in 1918, on Dean and 

 Monat's egg medium, to which a few drops of blood had been added, 

 and on blood-clot medium. The media were inoculated with blood 

 and mucus from motions passed not longer than three hours, and 

 were incubated at 28°-30° C. In culture the amoebae varied from 

 8-30 microns in size, with homogeneous but often vacuolated cyto- 

 plasm containing ingested red blood cells and moving typically like 

 L. histolytica. Uninucleate and binucleate forms were seen. Cysts 

 were obtained by ceasing to subculture for two to three days and 

 then placing the culture for two hours in an ice-chest. 



Cysts from the culture produced typical dysenteric lesions in 

 cats by feeding and by inoculation high into the rectum by means of 

 a catheter. 



Strains. — -Vide historical section (p. 313). 

 >| Pathogenicity. — L. histolytica is the cause of amoebiasis in man 

 and animals, causing amoebic dysentery and amoebic abscesses in 

 the liver and other parts of the body. 



Loeschia gingivalis Gros, 1849. 



Synonyms. — -Amceha gingivalis Gros, 1849; A. buccalis Sternberg, 

 1862; A. dentalis Grassi, 1879; ^- dentalis Braun, 1883; Entamoeba 

 buccalis Prowazek, 1904; A. maxillaris Kartulis, 1906. 



Definition. — ^Loeschia with cysts containing only one nucleus, 

 cytoplasm often containing red blood-corpuscles, ectoplasm only 

 visible during motion as a clear highly refractive layer. Nucleus 

 as a rule not visible. Reproduction only by simple fission. 



History.— This amoeba, which occurs in the mouth in healthy 

 and diseased conditions, was first described by Gros in 1849, and 

 was afterwards studied by Sternberg, Grassi, Prowazek, ^nd men- 

 tioned by Braun, and is probably the same as Kartulis' organism. 



Morphology.- — -Its size varies from 7-35 fmicrons, the average 

 being 12-20 microns. 



The ectoplasm is only well defined during movement, which is 



