372 Hydrophobia, Lyssa, or Rabies 



the skin can be shaved), the scalp is washed with an antiseptic 

 solution and an incision about an inch long is made and the skull 

 exposed. With a small trephine a button of bone is cut out and the 

 dura exposed. The suspension of nervous tissue is drawn up in a 

 sterile hypodermic syringe, and one or two drops of it injected be- 

 neath the dura mater or deeply into the brain tissue. If the opera- 

 tion be successful the wound heals and no meningitis follows, but at 

 the end of about six days the rabbit becomes paralyzed, "dumb 

 rabies." Several rabbits should be simultaneously inoculated as 

 should a single rabbit develop meningitis, through accident or bad 

 technic, no information is gained, and no diagnosis is possible. 

 The rabid rabbits die in a day or two after the onset of the palsy, and 

 Negri bodies can be found in the brain tissue, which is infectious for 

 other rabbits in endless series. 



3. The Histological Changes in the Nervous System. — These are 

 now rarely looked for, as experience has shown them to be the least 

 reliable means of making the diagnosis. The chief changes are the 

 "tubercles of Babes,"* which consist of perivascular collections of 

 cells, and collections of newly formed cells about the ganglionic 

 nerve-cells of the brain and cord. 



Van Gehuchten and Nelis,t and Ravenel and McCarthy { have 

 studied these lesions. Ravenel and McCarthy think that Babes 

 gave undue prominence to the rabid tubercle, which consists of an 

 aggregation of embryonal cells about the central canal of the cord, 

 about the ganglionic nerve-cells, and about the capillary blood- 

 vessels. They think, however, that the lesions of the nerve-ganglion 

 cells are pathognomonic if taken in connection with the clinical 

 manifestations of the disease. The specific changes consist of de- 

 generation, chromatolysis and even total disappearance of the nuclei 

 of the ganglion cells, dilatation of the pericellular space, and invasion 

 not only of this space, but also of the nerve-cells by embryonal cells, 

 and at the same time the appearance of small corpuscles which are 

 hyaline, brownish and in part metachromatic. Spiller§ refused to 

 regard these lesions as pathognomonic of rabies and it is now gen- 

 erally conceded that they are not specific of rabies, and, therefore, 

 not to be looked upon as of more than confirmatory evidence of the 

 disease. 



Virulence. — The virus of rabies is variable in virulence to a 

 marked degree. "Street virus," or that obtained from rabid dogs, 

 is so variable that before scientific study with it is possible, it must 

 be standardized. This is done by passage through rabbits, the tech- 

 nic of the inoculation being the same as that given in the section 

 on "Diagnosis." After being passed successively from rabbit to 



* Ann. de I'lnst. Pasteur, 1896, vi, 209. 



t "Univ med. Mag.," Jan., 1901. 



t "Archiv. de Biologie," 1900, xvi. 



§ "Pathological Society of Philadelpliia," March, 1901. 



