312 AGRICULTURAL BACTERIOLOGY 



by the bite of an infected animal. Many times the saliva 

 is so completely removed from the teeth of the rabid animal 

 that none of the organisms is introduced into the wound. 

 Especially is this likely to be true when the wound is in- 

 flicted through the clothing, through the coat of a long- 

 haired dog, or through the wool of a sheep. This is one of 

 the reasons why only a small proportion of the human be- 

 ings and animals that are bitten by rabid animals develop 

 the disease, even though no protective treatment is em- 

 ployed. 



The virus is known to be present in the saliva from two 

 to five days before the symptoms of the disease are evident. 

 The wounds in which the infection is most likely to be of a 

 serious nature are those inflicted on the head and face rather 

 than on the extremities. The virus develops in the nerves, 

 and is more likely to establish itself in tissues that are rich 

 in nerves than in those deficient in these structures. The 

 extent of the bites is also an important factor in determin- 

 ing whether infection is to occur, since the amount of virus 

 introduced will be in proportion to the number of bites 

 inflicted. The tissues seem to have the power of destroy- 

 ing a limited number of the organisms. Again, if the 

 wounds are such that bleeding is marked, there will be a 

 tendency for the organisms to be washed out. The deep 

 puncture wounds are likely to be more serious than a tear 

 in the flesh. 



It is commonly believed that there is a seasonal distribu- 

 tion of rabies, that it is more common during the so-called 

 dog days of late summer. There is little or no basis of fact 

 for this belief. There is, however, more opportunity for 

 the rabid dog to come in contact with human beings and 

 with animals in the summer than in the colder months when 

 there is less out-of-door life. The regulations that require 

 the muzzling of dogs for a few weeks in the summer have 



