126 BACTERIOLOGY. 



lowing, and spasm of the muscles of respiration. The 

 spasms are very painful and may be induced even by 

 the sight of water. This is the origin of the name 

 hydrophobia, which means fear of water. 



All efforts to find the cause of the infection in the 

 brain and spinal cord have been fruitless. Peculiar 

 bodies, called Negri bodies, are quite constantly found 

 in the brain and spinal cord, which many believe are 

 parasites belonging to the animal kingdom, and classed 

 as protozoa. The diagnosis of rabies can be made 

 either by finding the Negri bodies or by reproducing 

 the disease in rabbits by inoculating them in the brain 

 with portions of the spinal cord of rabid animals, 

 immunity j t j s due tQ the stuc jies o f Pasteur that we are able 



to immunize against rabies. He found that the virus 

 of rabid dogs could be intensified by inoculating a 

 series of rabbits until the inoculation period could be 

 shortened to six or seven days. The spinal cords of 

 rabbits inoculated in this way contain the virus in its 

 most concentrated form, and is spoken of as the fixed 

 virus. 



The fixed virus may be attenuated by drying 

 the spinal cords and, if human beings are now inocu- 

 lated with portions of the tissue, beginning first with 

 the most attenuated and then with more and more 

 virulent tissue, an active immunity is established. 

 This is the method now in use in the treatment of per- 

 sons who have been bitten by rabid dogs, and it can 

 be applied during the forty- to sixty- day incubation 

 period. It has proven very successful. In the last ten 



