16 HANDBOOK OF PROTOZOOLOGY 



portant contributions appear continuously. Since all parasitic 

 Protozoa must have originated in free-living forms, the com- 

 prehension of the morphology, physiology and development 

 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 and large 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 micro- 

 scope and in technique. 



Here again Leeuwenhoek, in 1681, seems to have been the 

 first to observe a parasitic protozoan, for he found Giardia 

 intestinalis in his own diarrhoeic stools. There is no record 

 of anyone having seen Protozoa living in other organisms until 

 1828, when Dufour's account of the gregarine from the intestine 

 of coleopterous insects appeared. Some ten years later, Hake 

 observed the oocyst of the coccidian, Eimeria stiedae, of rabbits, 

 without realizing its real nature. A flagellate was observed in 

 the blood of salmon by Valentin in 1841, and the frog trypano- 

 some was discovered by Gluge and Gruby (1842), the latter 

 author creating the genus Trypanosoma for it. 



The gregarines were a little later given attention by Siebold 

 (1839), KolHker (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 coccidian, Klossia helicina, in the excretary organ of Helix. 

 Eimer (1870) made an extensive study of Coccidia occurring in 

 various animals. Balantidinm coli was discovered by Malmsten 

 in 1856. Lewis in 1870 observed Entamoeba coli in India and 

 Losch in 1875 found Entamoeba histolytica in Russia. At the 

 beginning of the nineteenth century, an epidemic disease, 

 pebrine, of the silkworm appeared in Italy and France, and a 

 number of biologists became engaged in its investigation. 

 Foremost of all, Pasteur (1870) made an extensive report on the 

 nature of the causative organism, now known as Nosema bomby- 

 cis, and also on the method of control and prevention. Perhaps 



