PROTOZOA AND OTHER ANIMALS 977 



the cultures, which, with daily renewal of medium, were kept several 

 weeks, and, he stated, might be continued indefinitely. Entodin'mm lived 

 particularly well. 



The rumen ciliates, so far as is known, do not form cysts. Tropho- 

 zoites have been found in the mouth fluids (Becker and Hsiung, 1929), 

 and ruminants have been infected by giving this material with the food 

 (Mangold and Radeff, 1930). Natural transmission is by contact, in 

 common feeding, in which there is a certain period when the tropho- 

 zoites are exposed to the external environment (Becker and Hsiung, 

 1929; Mangold and Radeff, 1930; Strelkow, Poljansky, and Issakowa- 

 Keo, 1933). Their ability to withstand external conditions is therefore 

 of crucial significance. The holotrichs and Entodinium are more re- 

 sistant than the larger Ophryoscolecidae. Strelkow et at. reported that 

 after six hours at room temperature all ciliates were still active, and 

 many survived longer. At 0° C. all continued normal activity for an 

 hour. On dilution of the rumen fluid, they survived for various periods 

 of from one to thirty-two hours; and most were alive after six hours in 

 material two-thirds evaporated. They are thus clearly able to live long 

 enough on feed or in water to infect other animals using the same con- 

 tainers. The interesting report of Fantham (1922) that "species of 

 Entodinium and Diplodiniutn may be found on wet grass and in aque- 

 ous washings of fresh grass and even of dried grass (fodder) from 

 sheep runs and pasturage" leaves the reader desirous of details con- 

 cerning his observations. 



It has been found to be a simple matter to bring about elimination of 

 the ciliates from the rumen and the reticulum. Modern investigators 

 have used three defaunation treatments. Mangold and his coworkers 

 have found starvation alone to be satisfactory. The ciliates may ap- 

 parently be absent after only three or four days, but Dogiel and Wino- 

 gradowa-Fedorowa (1930) found six to seven days without water 

 necessary for complete defaunation. They found preferable, however, 

 partial feeding with dry food and water and a liter of milk daily. Milk 

 feeding was used by Falaschini (1935). On the basis of studies made 

 on material kept in the thermostat. Mangold and Usuelli (1930) con- 

 cluded that the increased acidity induced in the rumen contents is re- 

 sponsible for the incompatibility of milk and ciliates. The best method 

 of defaunation. according to Strelkow, Poljansky, and Issakowa-Keo 



