NATURE OF POLYHEDRAL BODIES FOUND IN INSECTS. 375 



the coarser Berkefeld and Chamberland filters, and these filters 

 exclude the Negri bodies. The most generally accepted view 

 at present is that the Negri body is a cellular reaction against the 

 invasion of the filterable virus. The virus of hydrophobia has 

 not been cultivated. 



VARIOLA AND VACCINIA (SMALLPOX AND COWPOX). 



In 1892 Guarnieri described certain cellular inclusions in 

 variola and vaccinia which are specific for these two diseases. 

 The bodies are from 1-8 /x in diameter, and round, oval, or sickle- 

 shaped. They lie in the cellular spaces, often in close proximity 

 to the nucleus, and can be demonstrated in vaccine pustules as 

 well as in the experimental lesions produced in the rabbit's 

 cornea. The virus of variola and vaccinia passes through the 

 coarser porcelain (Chamberland) filters. Most authorities regard 

 the Guarnieri bodies as the effect of a specific reaction of epi- 

 thelial cells against the virus. The virus has not been cultivated. 



TRACHOMA. 



In trachoma certain granules are found in the cytoplasm of 

 the inflamed epithelial cells which cover the conjunctiva. Bodies 

 similar to the trachoma bodies have also been found in other 

 inflammations of the conjunctiva, and are therefore thought 

 not to be specific of trachoma. The trachoma bodies are re- 

 garded as the product of mucous secretion under pathological 

 conditions. The virus passes through Berkefeld filters. It has 

 not been cultivated. 



Cellular inclusions not regarded as parasitic by some workers 

 have been found in a number of other diseases. In scarlet 

 fever cellular inclusions occur in the skin lesons; in foot and 

 mouth disease inclusions are found in the vesicles; in fowl pest 

 inclusions are found in the brain and in epithelioma contagiosum 

 or fowl diphtheria in the epithelium. Cytoplasmic inclusions 

 accompanying many of the diseases of higher animals, and re- 

 garded as non-parasitic in most cases are not at all uncommon, 

 but we have been unable to find any account in the literature of 

 vertebrate diseases which are accompanied by the formation of 

 nuclear inclusions as is the case with the polyhedral diseases of 

 insects. 



