INTRODUCTION 15 



and its relation to the occurrence of fever and was able to distinguish 

 two types of fever. MacCallum (1897-1898) found in the United 

 States the union of a microgamete and a macrogamete of Haemopro- 

 teus of birds. Almost at the same time, Schaudinn and Siedlecki 

 (1897) showed that anisogamy results in the production of zygotes in 

 Coccidia. The latter author published later further observations on 

 the life-cycle of Coccidia (1898, 1899). 



Ross (1898) showed how Plasmodium relictum (P. praecox) was 

 carried by Culex fatigans and described its life-cycle. Since that time 

 several investigators have brought to light important observations 

 concerning the biology and development of malarial organisms and 

 their relation to man. In the present centur}'^, Forde and Button 

 (1901) observed that the sleeping sickness in equatorial Africa was 

 due to an infection by Trypanosoma gambiense. In 1903 Leishman 

 and Donovan recognized Leishmania of "kala-azar." 



Artificial cultivation of bacteria had contributed toward a very 

 rapid advancement in bacteriology, and it was natural, as the num- 

 ber of known parasitic Protozoa rapidly increased, that attempts to 

 cultivate them in vitro should be made. Musgrave and Clegg (1904) 

 cultivated, on bouillon-agar, small free-living amoebae from old 

 faecal matter. In 1905 Novy and McNeal cultivated successfully the 

 trypanosome of birds in blood-agar medium, which remained free 

 from bacterial contamination and in which the organisms underwent 

 multiplication. Almost all species of Trypanosoma and Leishmania 

 have since been cultivated in a similar manner. This serves for de- 

 tection of a mild infection and also identification of the species in- 

 volved. It was found, further, that the changes which these organ- 

 isms underwent in the culture media were imitative of those that 

 took place in the invertebrate host, thus contributing toward the 

 life-cycle studies of them, 



Bass (1911), and Bass and Johns (1912) demonstrated that Plas- 

 modium of man could be cultivated in vitro for a few generations. 

 During and since the World War I, it became known that numerous 

 intestinal Protozoa of man are widely present throughout the tropi- 

 cal, subtropical and temperate zones. Taxonomic, morphological and 

 developmental studies on these forms have therefore appeared in 

 an enormous number. Cutler (1918) seems to have succeeded in 

 cultivating Entamoeba histolytica, though his experiment was not 

 repeated by others. Barrett and Yarborough (1921) cultivated 

 Balantidium coli and Boeck (1921) cultivated Chilomastix mesnili. 

 Boeck and Drbohlav (1925) succeeded in cultivating Entamoeba 

 histolytica, and their work was repeated and improved upon by sev- 



