MICROBIAL DISEASES OF MAN AND ANIMALS. 689 



nineteenth century, it appeared in the south of France. Pasteur studied 

 the disease and discovered its cause. He perceived that pebrine might 

 be prevented by destroying infected eggs and by rearing silk worms 

 from only those eggs which could be seen, with a microscope, to be free 

 from Microsporidia. His advice was followed and the French silk industry 

 was freed from a plague which had almost destroyed it. 



INFUSORIA. 



Most of the parasitic infusoria occur in the alimentary tracts of their hosts 

 Harmless infusoria are found in the stomachs of all herbivorous animals; they 

 are also found in frogs' intestines. Balantidium coli is often a harmless parasite, 

 but it may cause a severe inflammation of the intestine in men and in swine; 

 one or two other infusoria occasionally produce similar symptoms in man. 

 Other species of infusoria are parasitic on fish; some of these are harmless; 

 others, by finding their way into the gills or beneath the scales, cause serious 

 diseases. 



BALANTIDIUM ENTERITIS. 

 Balantidium coli. 



Balantidium coli is the most important of the infusoria parasitic to man; it may 

 be a cause of dysentery. 



This organism measures about 150/4 in length and 50/4 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 division, either with or 

 without a precedent conjugation. It may encyst, and it is with this form of the parasite 

 that infection by it is contracted. 



High enenfata of mild antiseptics will cure infections by this parasite. 

 PARASITES OF UNCERTAIN POSITION. 



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

 tuberculosis, which is caused by a protozoon called Histoplasma capsulatum. 

 The only known stage of this parasite greatly resembles the non-motile form of 

 Herpetomonas donovani; but it contains only one, not two masses of chromatin. 

 This organism is certainly a protozoon; although the genus to which it belongs 

 cannot be determined. 



CHLAMYDOZOA. 



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 parasites, 

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