280 CARNEGIE INSTITUTION OF WASHINGTON, 



Substantial progress has been made in the fuller study of variation within 

 the several species of amoeba parasitic in man, with a view to the more 

 accurate delineation of their normal range of form during the processes 

 of cell-division and encystment. 



Medical literature has for many years contained accounts of flagellate 

 diarrhoeas attributed to Trichomonas. This literature is conflicting, and 

 the pathogenicity of these flagellates has been generally denied in recent years 

 with the resulting confusion of testimony as to the significance of these infec- 

 tions. We have, during the past year, had access to three cases of infection 

 by the trichomonad flagellate which has been described as Pentatrichomonas 

 ardin delteili from Algiers, Calcutta, and Manila. It is undoubtedly a 

 pathogenic organism in the cases now under our observation. We have been 

 able to clearly establish the fact that there are two types of trichomonad 

 infections of man, one of which {Pentatrichomonas) is undoubtedly patho- 

 genic, and we have been able to establish the characteristics by which it may 

 be distinguished from the non-pathogenic form in life and in stained material. 

 This rests upon the differential behavior of the flagella in life which hitherto 

 has obscured the constancy of the differential numbers of flagella in the two 

 genera. 



In cooperation with Dr. J. F. Kessel, University of California Fellow in 

 Zoology, parasitic amoebic infections of culture rats and mice have been 

 studied. Three species have now been clearly diagnosed and their chromosomes 

 counted in two cases. These two belong to our genus Councilmania. As a 

 result of Dr. Kessel's experiments certain human parasitic protozoan infec- 

 tions have been successfully implanted in the intestine of culture rats and 

 mice. This has been accomplished by the elimination of milk diet, the use of 

 young rats after weaning, and the limitation of experimental infection to 

 rats previously known to be free from their own species of amoeba. Dr. 

 Kessel has perfected a method of determining amoeba-free rats by the use of 

 epsom salts. This work adds a new weapon to the experimentalist in the 

 attack upon the experimental study of human parasitic protoza. In con- 

 junction with Dr. Kessel the experimental transfer of the human infections to 

 the rat have enabled us to clearly establish the generic and specific identity 

 of Councilmania lafleuri and the constancy of the characters which differen- 

 tiate it from Endamoeha coli. 



This is a matter of greatest clinical significance, since Councilmania has 

 clear pseudopodia and this characteristic is very generally used at the present 

 by clinical microscopists to diagnose Endamoeba dysenterice, the etiological 

 factor in human amoebiasis. The presence of Councilmania would, there- 

 fore, lead to false diagnosis, if reliance is placed upon clear pseudopodia. It 

 will be necessary in the future, and will now be possible, to guard against this 

 mistaken diagnosis. 



The study of Giardiasis in dogs and the transfer of human infections by 

 Giardia enterica to the dog have been successfully accomplished in dogs by 

 Miss Howitt in our laboratory. It is highly probable that the dog may prove 

 to be a carrier for this human infection, especially in children. Studies are 

 now being conducted in experimental therapeutics of these Giardia infections 

 in dogs. 



Dr. Olive Swezy has assisted in the work with these human infections. 



