14 PROTOZOOLOGY 



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

 investigators have brought to light imi)ortant observations con- 

 cerning the biology and development of these organisms and their 

 relation to man. In the present century, Forde and Dutton (1901) 

 observed that the sleeping sickness in Africa is due to an infection 

 by Trypanosoma gamhiense. In 1903 Leishman and Donovan 

 recognized Leishmania of "kala-azar." 



Artificial cultivation of bacteria had contributed toward a very 

 rapid advancemtnt in bacteriology, and it was natural, as the 

 number of known parasitic Protozoa rapidly increased, that at- 

 tempts to cultivate them in vitro should be made. Musgrave and 

 Clegg (1904) cultivated, on bouillon-agar, small free-living amoe- 

 bae from old fecal 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 detection of a mild infection and 

 also identification of the species involved. It was found, further, 

 that the changes which these organisms 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 

 Plasmodium of man could be cultivated in vitro for a few genera- 

 tions. During and since the World War, it became known that 

 numerous intestinal Protozoa of man are widely present through- 

 out the tropical, 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. Barret and Yarborough 

 (1921) cultivated Balantidium coli and Boeck (1921) also culti- 

 vated Chilomastix mesnili. Boeck and Drbohlav (1925) succeeded 

 in cultivating Entamoeba histolytica, and their work was repeated 

 and improved upon by several investigators. While the cultiva- 

 tion has not yet thrown much light on this and similar amoebae, 

 it reveals certain evidences that there is no sexual reproduction in 

 these amoebae. Since that time, almost all intestinal Protozoa of 

 both vertebrates and invertebrates have been cultivated by nu- 

 merous investigators. 



