168 PROTISTS AND DISEASE 



as sporozoa I was studying fungi and calling them protozoa 

 all the time, i.e. for nearly 30 years ; and this has been the 

 case generally, with the result that we have importuned 

 protozoologists for enlightenment, which could only have 

 been given us by cryptogamic botanists. 



Smallpox 



Guarnieri's experiment. Twelve hours after inoculation 

 of a scratch in the corneal epithelium of any rodent with 

 smallpox or vaccine lymph minute foreign bodies can be 

 found close to the nuclei of the epithelial cells. With the 

 point of a sharp knife or needle a linear scratch is made 

 vertically across the cornea through the epithelium without 

 incising the fibrous layer. At the desired time the animal is 

 killed, the eyeball excised and placed at once in the fixing 

 fluid, or scrapings can be made for immediate examination. 

 This is Guarnieri's experiment. 



After 24 hours the corpuscles are larger and the experi- 

 ment can be used for diagnosis, scrapings showing the bright 

 greenish bodies clearly. At this stage sections show that 

 the bodies in cells close to the incision are larger than those 

 farther away, those in cells next the apparently uninfected 

 ones being very small, many of them subdividing by fission. 



At the end of 48 hours the bodies are very obvious and 

 in well-stained sections show very clearly as in Fig. 47. 

 They stain well with methylene blue and with haematoxylin 

 and eosin, taking the basic and acid stains about equally. 



