RABIES 303 



The Commission demonstrated that two species of hosts are 

 necessary for the life cycle of the parasite, human beings and 

 mosquitoes, and that under natural conditions it is transmitted 

 from infected to healthy individuals only by the bite of a small 

 mosquito, JEdes calopus, first spoken of as Stegomyia. After being 

 bitten a period of about five days elapses before the parasite appears 

 in the blood of the individual and remains there only during the 

 three succeeding days. Thus an infected mosquito must necessarily 

 have sucked the blood of a patient during the first three days of 

 his illness. An infected mosquito does not transmit the parasite 

 until at least twelve days after it has bitten the first patient. 

 Yellow fever can be produced in man under artificial conditions 

 by injecting the blood of a patient taken during the first three days 

 of illness or even by inoculation with the serum of such a patient 

 after it has passed through a fine Berkefeld filter. 



Noguchi has recently announced the visibility of the parasite 

 by dark field illumination and the possibility of its culture. 



Rabies or Hydrophobia. The disease occurs occasionally 

 amongst most carnivora. It is transmitted to man usually by the 

 bite of a dog. Experiments have shown that the virus is contained 

 in the saliva from twenty-four to forty-eight hours before symp- 

 toms appear. In man the incubation period after being bitten 

 varies from fourteen days to seven months, the rapidity with which 

 the disease develops being governed by the amount of virus 

 introduced, the point of inoculation, and the individual degree of 

 susceptibility. It has been frequently observed that in wounds 

 inflicted where the skin is thick and the nerves are few, or where 

 the clothing has afforded some degree of protection, the incubation 

 period is relatively long, whereas in wounds in parts more abun- 

 dantly supplied with nerves the incubation period is much shorter 

 and the disease usually more virulent. The symptoms of rabies 

 generally begin with pain in the wound, extending along the nerves 

 in the limb bitten, followed by a stage of nervous irritability, diffi- 

 culty in breathing and swallowing due to spasmodic contraction 

 of the throat muscles, and a marked increase in the flow of saliva. 

 Very soon the convulsive attacks become more or less general 



