12 PROTOZOOLOGY 



In the first year of the present century, Calkins in the United 

 States and Doflein in Germany wrote modern textbooks on pro- 

 tozoology deahng with the biology as well as the taxonomy. Cal- 

 kins initiated the so-called isolation pedigree culture of ciHates 

 in order to study the physiology of conjugation and other phe- 

 nomena connected with the life-history of the ciHates. The appli- 

 cation of this method has been found very popular in recent 

 years. 



Today the Protozoa are more and more intensively and exten- 

 sively studied from both the biological and the parasitological 

 sides, and important contributions appear continuously. Since all 

 parasitic Protozoa appear to have originated in free-living forms, 

 the comprehension of the morphology, physiology, and develop- 

 ment of the latter group obviously is fundamentally important 

 for a thorough understanding of the former group. 



Compared with the advancement of our knowledge on free- 

 living Protozoa, that on parasitic forms has been very slow. This 

 is to be expected, of course, since the vast majority of them are 

 so minute that the discovery of their presence has been made 

 possible only through improvements in the microscope and in 

 technique. 



Here again Leeuwenhoek seems to have been the first to ob- 

 serve a parasitic protozoan, for he observed, according to Dobell, 

 in the fall of 1674, the oocysts of the coccidian, Eimeria stiedae, 

 in the contents of the gall bladder of an old rabbit; in 1681, 

 Giardia intestinalis in his own diarrhcsic stools; and in 1683, 

 Opalina and Nyctotherus in the gut contents of frogs. There is 

 no record of anyone having seen Protozoa living in other organ- 

 isms until 1828, when Dufour's account of the gregarine from the 

 intestine of coleopterous insects appeared. Some ten years later, 

 Hake rediscovered the oocysts of Eimeria stiedae. A flagellate was 

 observed in the blood of salmon by Valentin in 1841, and the 

 frog trypanosome was discovered by Gluge and Gruby (1842), the 

 latter author creating the genus Trypanosoma for it. 



The gregarines were a httle later given attention by Siebold 

 (1839), Kolliker (1848) and Stein (1848). The year 1849 marks 

 the first record of an amoeba being found in man, for Gros then 

 observed Entamoeba gingivalis in the human mouth. Five years 

 later, Davaine found in the stools of cholera patients two flagel- 

 lates (Trichomonas and Chilomastix). Kloss in 1855 observed the 



