zz8 



THE QUARTERLY REVIEW OF BIOLOGY 



species of flagellates are both rare and 

 apparently harmless. The human coc- 

 cidium, Isospora hominis, is always patho- 

 genic but is rare and the diarrhea it pro- 

 duces is of short duration and not lethal. 

 The ciliate, Balantidium coli, is the agent 

 of balantidial dysentery, which may be 

 fatal to the host, but is not of frequent 

 occurrence. 



The blood-inhabiting protozoa of man 

 are three species of trypanosomes (Masti- 

 gophora), three species of leishmanias 

 (Mastigophora), and three species of 

 malarial parasites (Sporozoa). These are 

 all pathogenic and of great importance 

 where they occur, but are more or less 

 local in their distribution. The trypano- 

 somes cause Gambian sleeping sickness 

 (Trypanosoma gambiense) and Rhodesian 

 sleeping sickness (T. rhodesiense) in tropical 

 Africa, and Chagas' disease (T. cru^t) in 

 certain parts of South America. The 

 leishmanias cause kala-azar (Leishmania 

 donovani) in parts of Asia, Africa and 

 Europe, oriental sore (L. tropica) in 

 certain regions of Asia and Africa, and 

 South American leishmaniasis (L. bra^il- 

 knsis) in South America. The three 

 species of malarial parasites, Plasmodium 

 vivax of tertian malaria, P. malariae of 

 quartan malaria, and P. falciparum of 

 estivo-autumnal malaria, occur in tropical 

 and scmitropical regions throughout the 

 world. 



Protozoa were first discovered in man 

 by Leeuwcnhoek in 1681. Among the 

 many protozoa described by this famous 

 Dutch microscopist were flagellates, that 

 we now know as giardias, which he 

 encountered in his own stools. However, 

 free-living species were the first to receive 

 attention from biologists, and only com- 

 paratively recently have parasitic species 

 attracted investigators. Such discoveries 

 as that of the parasite of amoebic dysentery 

 by Loesch in 1873 (Loesch, 1875), °£ tne 



malarial parasite by Laveran in 1880 and 

 of a human trypanosome by Forde in 

 1901 (Forde, 190Z) stimulated thousands 

 of investigators to enter the field of 

 protozoology and has resulted in a large 

 body of knowledge regarding the parasitic 

 species, especially those that live in man 

 and domesticated animals. 



Protozoa were first reported from 

 monkeys about the year 1899 when 

 Laveran named a species of malarial 

 parasite, Plasmodium kochi, that Koch had 

 discovered in 1898 in Africa. Trypano- 

 somes were noted in the chimpanzee by 

 Ziemann in 190Z; the ciliate, Balantidium 

 coli, in orang-utans by Brooks in 1903; 

 amoebae in a macaque, Macacus pileatus, 

 by Castellani in 1908; and intestinal 

 flagellates in another species of macaque, 

 Macacus cynomolgus, by Noc in the same 

 year. During the succeeding twenty years 

 protozoa resembling almost every species 

 known to live in man have been recorded 

 from monkeys. It was not, however, 

 until about 19Z0 that investigators at- 

 tempted to determine by experiment 

 whether the protozoa of monkeys and 

 man belong to the same or to different 

 species. Recently many cross-infection 

 and cultivation experiments have been 

 carried out, but we are still very much in 

 doubt regarding the host-parasite speci- 

 ficity of monkey protozoa. 



AMOEBAE OF MONKEYS AND MAN 



At least eleven species of amoebae 

 belonging to three genera have been 

 described from monkeys. Nine of these 

 have been placed by their discoverers in 

 the genus Endamoeba and one each in the 

 genera Endolimax and lodamoeba. The 

 endamoebae all fall into two types that 

 correspond to two of the common species 

 living in man, namely, Endamoeba coli 

 with cysts containing 8 nuclei (fig. zb), 

 and E. histolytica with cysts possessing 



