Anatomical Changes, Symptoms. 



473 



Aecording to Kolesmkoff and Babes, there exists in the immediate neighbor- 

 hood of the motor center of the medulla oblongata and the motor cells of the 

 spinal cord, an accumulation of small round cells, which also invade the plasma of 

 the nerve cells and cause degeneration and atrophy. Babes considers these foci 

 as characteristic of rabies (rabic tubercles) as they were present in 389 cases of 

 rabies and absent in 35 other cases, but, according to Bohl, such changes are 

 sometimes also found m cases of distemper. 



Symptoms. The 

 period of incuba- 

 tio^ of rabies after 

 a natural infection 

 is generally sev- 

 eral weeks, but 

 may extend to 

 some months. Its 

 duration is in- 

 fluenced by the vir- 

 ulence of the virus, 

 the distance of the 

 place of infection 

 from the central 

 nervous system, 

 and the age of the 

 animal. Generally 

 the first symptoms 

 appear 2 to 8 weeks 

 after the bite ; 

 sometimes, how- 

 ever, they occur as 

 early as the end of 

 the second week or 

 again only after several months and as late as 1 to 2 years. 

 In dogs and swine the period of incubation is generally 

 brief (frequently only 10 to 15 days) ; in horses and cattle it is 

 longer (mostly 1 to 3 months). The disease develops earlier 

 in young animals than in old ones. 



Fig. 74. Rabies. Cervical ganglion of a dog affected 



with rabies. The nerve cells are partly atrophied, and in 



their place clumps of round cells appear. (After Van 



Glehuohten & Nelis). 



Concerning the duration of the period of incubation, Bouley, Haubner, and 

 Ziindel have gathered numerous statistical data. According to a compilation by 

 Eoll, the periods of incubation were as follows: Dogs: according to Bouley (144 

 cases) in 43% less than 30 days, in 40% between 30 and 60, in'l4% between 60 and 

 90 days, and in 3% between 4 and 12 months. According to Haubner (out of 200 

 dogs) in 83% less than 2 months, in 16% 9 to 12 weeks, in 1% 13 to 16 weeks, 

 and in only a few 7, 8, and 24 months. Horses: According to Bouley (out of 23 

 horses) in 1 more than 1 month, in 11 from 2% to 3 months, in 3 more than 100 

 days; according to Ziindel (out of 121 cases) in 28% less than 1, in 46% less 

 than 2, in 9% less than 3 months, and in the rest more than 3 months. Cattle: 

 According to Ziindel (out of 579 animals), in 5% less than 15 days, in 23% 15 

 to 30, in 39% 30 to 45, in 13%\ 45 to 60 days, in 17% 3 to 6 months, and in 

 1 case each 42 and 95 weeks; according to Hauber (out of 234 cases), in 82% 

 less than 3 months, and in 18% 4 to 9 months. Sheep and Goats: According 

 to Ziindel (out of 188 sheep), in 6% less than 15 days, in 41% 15 to 21, in 10% 

 21 to 80, in 26% 30 to 45, in 2% 45 to 60 days, and in 7% still longer. Out of 

 20 goats, in 15%i less than 20, in 60% 20 to 60 days, and in 25% longer. 

 Swine: According to Ziindel (out of 123 hogs), in 3% less than 8 (?), in 8% 

 8 to 15, in 51% 15 to 30, in 27% 30 to 60 days, and in 11% still longer. According 

 to the observations of the official Prussian veterinarian, the average period of 



