1922] McDonald: On lialantidmm coll and Balantidium suis 245 



ACKNOWLED(JMENTS 



It lias bct'u my privilege to study the morphology of Balantidium 

 coli and Balantidium sui^s (sp. nov.) under the direction of Professor 

 Charles A. Kofoid, to whom I am indebted for helpful suggestions and 

 for oversight of the entire vi^ork. Acknowledgment is due Professor 

 William W. Cort for many valuable critieisias. I also take this oppor- 

 tunity to express my appreciation of the courtesy of Mr. R. B. Brown, 

 superintendent of the Oakland Meat and Packing Company, who 

 kindly granted me permission to work in the company's abattoir and 

 also facilitated the work in every jjossible way. 



MATERIAL AND TECHNIQUE 



The material for th('S(! studies was obtaini^d almost exclusively from 

 pigs killed by the Oakland Meat and Packing Company, Stockyards, 

 California. At their abattoir I was permitted to work in the room 

 where the pigs were dressed, which made it possible to obtain llie 

 material from the intestine before it had cooled below the normal body 

 temperature. To determine the presence of the balahtidia a small slit 

 was made in the caecum and a drof) of the contents withdrawn witli 

 a pipette. This drop was (juickly placed on a warm slide and exam- 

 ined with a microscope. If the animals were present they would ])e 

 detected very readily for they are exceedingly active ; in most cases 

 they occurred in numbers sufficiently large that from one to ten could 

 be seen in everj' field when a 16 mm. objective was used. This method 

 was rapid enough to allow all pigs to be examined as fast as they were 

 killed and dressed. 



A sample from the caecum was not relied upon as critical in the 

 determination of infection until examination of the entire length of 

 the intestine had been made in several in>stances. In order to discover 

 the normal distribution throughout the intestine it was removed entire 

 and taken to the laboratory of the abattoir. Incisions were made every 

 one or two feet, beginning with the duodenum and continuing to the 

 rectum, and samples examined from each of these incisions. In no 

 cases were balantidia found more than three feet above the ileocaecal 

 valve, and onh' in two or three instances were any at all present in 



