200 DISEASES OF UNKNOWN ETIOLOGY 



immunity against subsequent infection with that disease. 

 Jenner, in 1798, was the one who first developed the principle 

 of using cowpox in the protection against human variola. 

 The exact cause of smallpox is not known. It is supposed to 

 spread by contact either directly with the sick or indirectly 

 by objects having been in contact with them. Such objects 

 are called fomites. Bacteria are present in the pustules 

 caused by vaccination and in the eruption of smallpox, but 

 they have been proved to be secondary invaders. The virus 

 is in the eruption or the scales and all discharges from the 

 body which should therefore be disinfected. 



Varicella or Chicken-pox. This is one of the eruptive 

 infections characterized by moderate fever and catarrhal 

 symptoms, but especially by a papular rash which becomes 

 vesicular then pustular, only to dry up and disappear rapidly. 

 The condition is of trifling moment and leaves no serious 

 sequelae; occasionally shallow pock marks remain. The 

 cause is unknown but probably is present in the skin lesions 

 only early in the eruption and passes directly from person to 

 person by freshly contaminated articles. Patients should 

 be kept away from non-immunes until all eruption has 

 disappeared. It is only necessary to disinfect discharges 

 from lesions and nasal and buccal secretions. 



Rabies or Hydrophobia. This is an acute infectious disease 

 to which nearly all animals are susceptible, characterized 

 by slowly progressive palsies and delirium. Hydrophobia 

 means fear of water. Such an emotion does not exist, but 

 animals merely avoid water because they cannot swallow it. 

 The cause of rabies is excreted in the saliva and may be trans- 

 mitted by the bite of a rabid animal, or by getting the saliva 

 into an open wound. The virus is innocuous if swallowed. 

 After having entered the body the virus travels to the central 

 nervous system and remains there throughout the whole 

 attack. The spinal cord particularly is involved. The only 

 evidence there is of the actual causative germ is the presence 

 of minute stainable granules in the nerve cells of the brain. 



