INTRODUCTORY 5 



the most rapid mode of diagnosing hydrophobia in the fresh cadaver 

 of a suspected animal, and by this means priceless time may be 

 saved in deciding whether Pasteur treatment is required by a bitten 

 person. 



It is remarkable that, after the lapse of fifteen years since 

 Guarnieri first described the Cytoryctes as a protozoon, biologists and 

 pathologists are still without any general agreement as to their 

 nature. The subject is one that requires the closest personal 

 application before anyone is justified in forming an opinion. Among 

 those who have worked longest at this subject is a biologist who 

 ranks among the foremost authorities on protozoa, Professor Calkins, 

 who has recently written : 



' Perhaps the majority of pathologists and some biologists are 

 opposed to this interpretation, and these bodies, like the Negri 

 bodies, are more commonly regarded as specific secretions or 

 degenerations than as protozoa. I have no doubt myself, from long 

 study of these organisms, that they are protozoa, and believe that, 

 with fresh material and by using the stain (Giemsa's) that Dr. 

 Williams has so successfully used for Neuroryctes, the last doubter 

 will be convinced.' 



Many other workers share this opinion, which I quote here 

 because it is one that none can afford to neglect, and it becomes the 

 more weighty when it is remembered that biologists, to whom classi- 

 fication is so important that they look with suspicion on anything 

 that is incertcz sedis, are apt to be more reluctant than patholo- 

 gists to accept biological discoveries in pathology. In this connection 

 we must remember that, had we waited for the position of the 

 Plasmodium malaria to be settled in classification before accepting it 

 as a protozoon, we should have been still waiting for that most 

 important piece of knowledge, which has done so much to ameliorate 

 the condition of thousands of human beings, and has opened up new 

 pathways in science. An outline of the chief recent contributions to 

 our knowledge of the Cytoryctes variola will be given below, a notice 

 of the Negri corpuscles, or Neuroryctes, being reserved for the next 

 part of this work. 



