690 MICROBIOLOGY OF THE DISEASES OF MAN AND ANIMALS. 



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 (p. 662), in Molluscum 

 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, measuring about 0.25/1 in diameter. They are spherical and occur within 

 the cells. In preparations stained by Romanowsky's method they are colored like 

 chromatin. 



ULTRAMICROSCOPIC VIRUSES (p. 64). 



