336 The Philippine Journal of Science im 



Stein (1862), Ekecrantz (1869), and Wising (1871) in the pigs 

 in Sweden, by Grassi (1882) in Italy, by Rapchevski (1882) 

 in Russia, by Railliet (1886) and by Newmann (1888) in France, 

 by Stiles (Strong, 1904) in the United States, and by Strong 

 (1904) in Manila. The examination of the fseces of a somewhat 

 limited number of pigs here convinces me that a large proportion 

 of them in the Philippine Islands are parasitized with this 

 protozoan. The balantidium found in the intestine of the pig 

 is generally considered not to produce any symptoms or lesions 

 in its host. 



The question of the identity or nonidentity of the balantidium 

 found parasitic in the pig with Balantidium coli of man has an 

 exceedingly important bearing on the endemiology and prophy- 

 laxis of balantidiasis. 



Wising (1885) and Grassi and Calandruccio (1888) were of 

 the opinion that the balantidium of the pig is a species distinct 

 from Balantidium coli of man. Wising states that the latter 

 species is smaller and does not become encysted, while the pig 

 balantidium is larger and usually appears in the fseces in the 

 encysted stage, Grassi and Calandruccio drew their conclusions 

 from the fact that they were unable to infect themselves with 

 the balantidium of the pig by the ingestion of the encysted para- 

 sites. On the other hand, recent authors are inclined to the 

 opinion that the balantidium of the pig and of man are one 

 and the same species, but no special evidence is advanced to 

 support this view. 



In consideration of the close domestic relations existing 

 between the pig and natives of the lower class, the fact that the 

 pig is the chief scavenger in these Islands, the prevalence of 

 balantidium as a parasite of the pig, and the fact that this 

 parasite is passed more or less constantly in the fseces of the 

 parasitized pig in the resistant encysted stage, make the identity 

 of the 2 species particularly important in explaining the preva- 

 lence of infections of man with Balantidium coli in the Philip- 

 pine Islands. 



The experimental infection of animals with Balantidium coli 

 has been attempted by many investigators. Brumpt (1909), 

 who found cases of natural infection of apes with Balantidium 

 coli in Indo China, reports that he was able to pass one of these 

 strains through 6 healthy monkeys, to parasitize a monkey with 

 balantidia obtained from the fseces of a pig, and to parasitize 

 pigs with the strain of balantidium from the monkey. The 

 incubation period of the parasite varied from two to seventeen 

 days. A diarrhoea developed in 1 of the parasitized monkeys 



