844 MICROBIOLOGY OF DISEASES OF MAN AND DOMESTIC ANIMALS 



herbivorous animals and also in the large intestine of the frog. 

 Balanfidium coU is a common and apparently innocuous parasite of 

 the caecum and large intestine of the pig, but it may cause a severe 

 inflammation of the large intestine in man which not infrequently 

 proves fatal. One or two other infusoria occasionally produce similar 

 symptoms in man. Other species of infusoria are parasitic on fish. 

 Some of these are harmless, but some by finding their way into the 

 gills or beneath the scales, cause serious diseases. 



Balantidium Enteritis 



Balantidium coli — Malmsten, 1857 ^ 



Balantidium coli is the most important of the infusoria parasitic in man and 

 may cause a form of dysentery. ' 



, This organism measures about isoit in length and 50/1 in breadth. It is covered 

 with cilia; its cytoplasm is differentiated to form oral and anal areas and it contains 

 digestive and contractile vacuoles. It multiplies by simple transverse division, 

 either with or without a precedent conjugation. It may encyst, and this is the 

 form in which the parasite is transmitted from one host to another. 



High enemkta of mild antiseptics have been used in the treatment 

 of this infection. 



Parasites or Uncertain Position 



In Panama, there is a disease of man, somewhat resembling one 

 form of tuberculosis, which is caused by a protozoon called Eistoplasma 

 capsulatum. The only known stage of this parasite greatly resembles 

 the non-motile form of Leishmania donovani; but it contains only one, 

 not two masses of chromatin. This organism is certainly a protozoon; 

 although the genus to which it belongs has not been determined. 



Chlamydozoa (Prowazek, 1907) 



This name is given to certain bodies because their presence excites the cell 

 containing them to produce a substance which surrounds them like a cloak. The 

 exact nature of these bodies is disputed; it is even doubtful whether they are para- 

 sites, or whether they are merely the expression of some morbid change, produced 

 in the cells, by an unseen virus which causes the disease. They have been found 

 in trachoma, a disease of the eyelids of man, in hydrophobia, in MoUuscum 

 contagiosum, a skin disease, in smallpox, in vaccinia, and in scarlet fever. They 

 are mentioned with the protozoa because, if they are parasites, they are probably 

 more nearly allied to the protozoa than to the bacteria. They are extremely small 

 bodies, some measuring only 0.25J11 in diameter. They are spherical and occur within 



