RABIES 841 



the latter against vaccine lymph. This fact, which was first shown by 

 Casagrandi and has also been observed by Rouget, and by Remlinger and 

 Osman Nouri, again demonstrates that the virus will pass through porcelain 

 or similar filters. 



Rouget experimented on ten heifers, by inoculating 40 c.c. of the filtrate beneath 

 the skin : the test inoculation was carried out a week later with glycerin lymph 

 with which controls were also inoculated. He obtained four positive results. 



SECTION VIII. THE VIRUS OF YELLOW FEVER. 



In yellow fever the blood is infective, and if inoculated into an healthy 

 man leads to the development of the disease (Reed, Carroll, Agramonte). 

 The disease is transmitted by a mosquito (Stegomyia fasciata) : after feeding 

 on the blood of a yellow fever patient this mosquito can infect a healthy 

 man. 



Reed, Carroll and Agramonte have shown that yellow fever is due to an 

 invisible micro-organism. From their experiments, which have been con- 

 firmed by those of Parker, Beyer and Pothier, Rosenau, Marchoux, Salimbeni 

 and Simond, it follows that serum or defibrinated blood from a case of yellow 

 fever diluted with an equal volume of water and filtered through a Berkefeld 

 or Chamberland F or B bougie will yield an infective filtrate. The virus 

 seems to pass through filters quite easily and in most cases a dose of the 

 filtrate corresponding to O5-1 c.c. of serum has been sufficient to cause 

 typical yellow fever in man. 



SECTION IX. THE VIRUS OF RABIES. 



(Hydrophobia.) 



Remlinger and Riffat-Bey have shown that the virus of rabies will readily 

 pass through a Berkefeld V and even a W or N and Chamberland F : their 

 experiments were carried out with the brain of a rabbit made into an emulsion 

 with 300 c.c. of water. Similar results have been obtained by di Vestea, 

 Schiider, Bertarelli and Volpino, de Blasi and Celli. 



Peculiar polychromatic structures never seen in normal tissues have been 

 described by Negri in the central nervous system of man and the' lower 

 animals which have succumbed to rabies. 



These structures, which are invariably intra-cellular, occur in the pyramidal cells 

 of the cornu ammonis, in the cells of Purkinje, in the cerebellum and in the large 

 cells of the cerebral convolutions : they are not found, or only very rarely indeed, 

 in the cells of the pons varolii and medulla oblongata. They are generally round or 

 oval and measure from 10-25/x in diameter: occasionally they are much smaller 

 and only measure 0.5-1/x or less. They stain an intense bright red by Fasoti'a 

 method. 



Fasoti's method. 1. Fix small pieces of the tissue for 24-48 hours in Foa's solu- 

 tion (Miiller's solution, 100 c.c. ; perchloride of mercury, 2 grams) or in acid per- 

 chloride (p. 189). 



2. Wash rapidly in water. Freeze and cut. If a precipitate be produced it can 

 be removed by washing in iodine- alcohol. 



3. Stain the sections for 5-10 minutes in 0'5 per cent, solution of eosin, heating 

 gently. Wash in water. 



4. Differentiate until +he sections acquire a pink tint in the following solution : 



1 per cent, aqueous solution of caustic soda, - 4 drops. 



90 per cent, alcohol, - -.50 c.c. 



Wash in water. 



5. Stain in a 0*25 per cent, aqueous solution of methylene blue until the sections 

 are pale violet in colour. 



