RABIES 389 
Remlinger and Riffat-Bey found that the virus would pass through 
a Berkefeld filter “V,” but its passage was not constant, as rabbits 
inoculated with the filtrate did not all die of rabies. The filter which 
he used held back the organism of chicken cholera, which was used as 
a check on the filter. Remlinger more recently stated that the virus 
will pass through the more porous Berkefeld filters only. 
Babes states that the Negri bodies are not always present. He 
seems to consider them as a product bf the reaction of the cells to the 
cause of the disease. 
Resistance of the virus. The virus is destroyed by drying and by 
the action of light. In dry air, protected from light and putrefaction, 
the virulence of the spinal cord of rabbits is destroyed in fourteen to 
fifteen days. When spread in thin layers it is killed by drying in from 
four to five days and by sunlight in about forty hours. The loss of 
virulence by drying is gradual but quite regular, which fact was taken 
advantage of by Pasteur in the preparation of his vaccine. 
The virus may he preserved in neutral glycerin at ordinary tempera- 
ture for a long time. Roux found that after four weeks in glycerin at 
30° C., the virus in a rabid brain had the same power as when per- 
fectly fresh. Moore found that rabbits inoculated with rabid brains 
that had been kept in glycerin from three to four weeks did not develop 
the disease as quickly as those that were inoculated with the freshly 
removed organ. 
Rabies virus is quite resistant to putrefaction. Galtier found the 
virus active in the central nervous system of rabbits that had been 
buried for twenty-three days, of sheep buried thirty-one days and of 
dogs buried forty-four days. Other observers have found it still 
active in animals buried for twenty-four days. 
It is destroyed completely by a temperature of 50° C. in one hour 
or 60° C. in one-half hour. It is uninjured by exposure to extreme 
cold, resisting the prolonged application of a temperature from 10 to 
20° C. below zero. 
Its activity is destroyed in one hour by a 5 per cent. solution of | 
carbolic acid, or by a 1 to 1,000 solution of corrosive sublimate. 
Water saturated with iodine destroys it in ten minutes. 
Method of invasion. When introduced into an animal either 
experimentally or by the bite of a rabid dog, the virus remains for a 
time without producing either local or general symptoms. The virus 
penetrates the nervous system by following the nerve trunks from 
the site of infection to the spinal cord, then through the spinal cord to 
