246 UNKNOWN CA USES OF OTHER INFECTIOUS DISEASES. 



How is it to be distinguished from the Old World hookworm, or Aukylos- 

 toma duodenale ? 



Describe its mode of entrance in the human body. How does it affect the 

 human body? What disease is caused by it? 



Describe its ova. Where are they found? 



CHAPTER XXVI. 



THE UNKNOWN CAUSES OF OTHER INFECTIOUS 

 DISEASES. 



IN rabies, yellow fever, scarlatina, and measles the organisms 

 whose etiological claims have been advanced are many and 

 varied. So far the claims of none are sufficiently advanced 

 or supported to demand treatment in this book. The finding 

 of the so-called " Negri" bodies and the method of immuniza- 

 tion introduced by the immortal Pasteur will be referred to in 

 connection with Rabies. The intermediary function of the Steyo- 

 myia mosquito in yellow fever is well known, and a knowledge 

 of the more distinctive features of this mosquito is desirable. 



BABIES. 



Rabies is an intensely fatal microbic disease, with an incu- 

 bation period, in ordinary cases, of from two weeks to two 

 months. In some cases incubation periods of six months have 

 been reported. Negri, in 1903, described certain bodies which 

 he observed constantly present in cases of rabies. He found 

 them in all parts of the brain, but particularly in the " hippo- 

 campus major" and " cerebellum. " These constitute, accord- 

 ing to a preponderance of authorities, a valuable means of 

 diagnosis in doubtful cases. They may be demonstrated in 

 section, stained with eosin and methylene-blue. They stain 

 pink, and may be recognized by their oval shape and average 

 length of about 1 5 /*. Fairly good preparations may be obtained, 

 generally by crushing a small piece of infected brain sub- 

 stance beneath the cover-glass and then staining with one of 



