202 THE ANIMAL PARASITES OF MAN 



regard Balantidia as the primary cause of the various diseases of the 

 large intestine, which often commence with the development of 

 ulcers, but they consider that they may aggravate these diseases and 

 render them obstinate. According to Solowjew, Askanazy, Klimenko 

 and Strong and Musgrave, however, the parasites penetrate the intes- 

 tinal wall, and give rise to ulcerations which may extend deeply into 

 the submucosa, and even be found in the blood and lymphatic vessels 

 of the intestinal wall. According to Stokvis, B. coli occurs also in 

 the lung ; at all events this author states that he found one living and 

 several dead paramaecia (?) in the sputum of a soldier, returned from 

 the Sunda Islands, who was suffering from a pulmonary abscess. 

 Sievers has shown that B. coli might occur in persons not suffering 

 from intestinal complaints, but E. L. Walker 1 (1913) states that every 

 person parasitised with B.. coli is liable sooner or later to develop 

 balantidian dysentery. 



Since Leuckart confirmed the frequent presence of B. coli in the 

 rectum of pigs, and corresponding observations were made in other 

 countries, the pig is universally considered to be the means of the 

 transmission of Balantidium to man. The encysted stages only serve 

 for transmission, because, according to all observations, the free 

 parasites have a very small power of resistance. They perish when 

 the faeces have become cool ; they cannot live in ordinary, slimy, or 

 salt water. As they are killed by acids even when much diluted, they 

 cannot pass through the normal stomach alive except under the most 

 unusual circumstances. The pigs, in whose intestines the Balantidium 

 appears to cause little or no disturbance, evacuate numerous encysted 

 Balantidia with the faeces, and their occasional transference to man 

 brings about their colonization there, but perhaps only when a disease 

 of the colon already exists. 



Experimental transmission of the free parasites to animals (per os 

 or per anum) yielded negative results, even in the case of pigs. 

 Casagrandi and Barbagallo (1896), however, had positive, as well as 

 negative, results. They employed healthy young cats, or cats in which 

 catarrhal entero-colitis had been artificially induced (which in other 

 experiments is apt to cause the death of the animals experimented upon 

 in about six or seven days), or finally cats that had dilatation of the 

 rectum with alkaline reaction of the faeces. An attempt to infect three 

 healthy cats by injecting human faeces containing Balantidium into the 

 rectum proved negative, in so far as the faeces of the experimental 

 animals had an acid reaction and contained no Balantidia, but at the 

 autopsy performed eight days after infection a few encysted parasites 

 were found in the mucus of the ileum. In the case of four cats 



1 Philip. JL St., Sec. B, viii, p. 333. 



