viii, B, 5 Walker: Experimental Balantidiasis 345 



6. Forty per cent of 5 monkeys fed or injected rectally with 

 Balantidium coli hominis became parasitized. 



7. Seventy and five-tenths per cent of 17 monkeys fed or 

 injected rectally with Balantidium coli suis became parasitized. 



8. Monkeys parasitized with either Balantidium coll hominis 

 or Balantidium coli suis show the parasities in the stools only 

 at infrequent intervals. 



9. Only a small proportion of the parasitized monkeys became 

 infected. Of 2 monkeys parasitized with Balantidimn coli homi- 

 nis, 1, and of 12 monkeys parasitized with Balantidium coli suis, 

 1, shoM^ed the parasites in the tissues post mortem. 



10. The early lesions of the intestine of monkeys infected with 

 Balantidium coli consist only of a slight hypersemia with or with- 

 out punctiform haemorrhages. 



11. Histological examination of the tissues of monkeys recently 

 infected with Balantidium coli show changes, notably vascular 

 dilation, minute haemorrhages, round-cell infiltration and eosino- 

 phiha, which distinguish them from lesions of bacterial origin. 



12. Balantidium coli was never found entering the tissues 

 through the lesions in 10 parasitized monkeys having a colitis 

 or ulcerations due to bacteria or other causes. 



13. In those monkeys in which infection took place, the 

 balantidia entered the tissues through the sound intestinal epi- 

 thelium. 



14. Balantidium coli can produce bacteriologically sterile ab- 

 scesses in the submucosa of an infected intestine. 



15. Balantidium coli is the primary etiologic factor in the 

 symptoms and lesions of balantidial dysentery. 



16. The latency prevalent in balantidiasis of man is due chiefly 

 to the fact that the patient, although parasitized, is not infected 

 with Balantidium coli, but in part to the chronicity of the ulcera- 

 tive process in infected cases. 



17. Every person parasitized with Balantidium coli is liable 

 sooner or later to develop balantidial dysentery. 



18. Baluntidium coli suis is identical with Balantidium coli 

 hominis. 



19. The domesticated pig is the chief source of infection in 

 the balantidiasis prevalent in the Philippine Islands, 



20. Therefore, efficient prophylactic measures against balan- 

 tidiasis in the Philippine Islands should be directed against these 

 animals, which should be confined and not allowed to run in 

 yards and dwellings. 



