1914] Sharp: Diplodinium ecaudatum 45 



Acknowledgments 



Whatever there be of merit in the methods used and the results 

 so far obtained is due to the kindly and helpful suggestions and 

 interest of Professor Kofoid, under whose direction the work has 

 been done. 



My acknowledgments are also due to Mr. R. B. Brown, Superin- 

 tendent of the Oakland Meat and Packing Company, for his personal 

 interest and assistance in procuring material for this study in the 

 most advantageous manner. 



Literature 



The literature upon this subject is not extensive, although covering 

 a period of more than seventy years. A brief review follows. 



The first information regarding the presence of protozoans in the 

 stomach of the ox was given by two French scientists, Grube and 

 Delafond (1843). In this communication they presented a short 

 general account of the stomach parasites of the horse, the dog, and 

 the pig, as well as those of ruminants. This work is important because 

 of the early date at which it was done and because it opened up a 

 new field of investigation. The results, according to our modern 

 conception, were by no means accurate, and the work, although carried 

 out with great skill, considering the limited means of that period, 

 is unfortunately unaccompanied by illustrations ; a fact which makes 

 it difficult to determine which protozoans the investigators observed. 

 In the case of the ox they gave descriptions of four species, from 

 which it is almost certain that they had observed those protozoans now 

 classified as belonging to the genera Ophryoscolex, Entodinium, 

 Diplodinium and IsotricJia. Even at this early date (1843) they 

 called attention to the fact that in the ox these protozoans occur in the 

 living condition only in the first two subdivisions of the stomach, 

 the rumen and the reticulum; while in the third and fourth sub- 

 divisions, the omasum and the abomasum, only dead and disintegrated 

 animals are found. 



The next information regarding these protozoans was given by 

 Colin (1854). In a discussion of the digestive processes which take 

 place in the stomachs of the ruminants Colin reproduces eighteen draw- 

 ings, but gives only brief descriptions. The figures demonstrate 

 clearly, however, that Colin saw and recognized species subsequently 

 described in the genera Diplodinium, Entodinium. and Isotricha. 



