INFECTIOUS DISEASES OF UNKNOWN CAUSATION 171 



Virulent spirochaeta are also present in the urine and feces of inoculated 

 animals. 



Spirochaeta icterohemorrhaga is anaerobic and facultative aerobic. Uhlen- 

 huth and Fromme cultivate it in tubes of rabbit serum diluted with normal salt 

 solution and cover this medium with.a layer of oil to exclude air. 



The serum of persons and animals, after recovery from Weil's disease, con- 

 'tains antibodies which will produce Pfeiffer's phenomenon when brought into 

 contact with spirochaeta icterohemorrhaga. 



GANGRENE 



The type of gangrene due to infection has been attributed to several bacilli 

 that were looked upon as most constantly associated with the disease and, there- 

 fore, probably a specific factor. 



It is now well established that gangrene due to infection may be produced by 

 a variety of organisms, the majority of which are obligate anaerobic. 



Small pox, scarlet fever, yellow fever and measles are all infectious dis- 

 eases caused by unknown microorganisms. 



Small Pox. The virus of this disease is present in the pustules that develop 

 on the skin of infected persons. One attack of the disease confers immunity. 

 Cow pox is a disease of cattle similar to small pox in man, and the virus of cow 

 pox is present in the pustules which develop on the epithelial surface of infected 

 animals. In 1798 Jenner discovered that the virus taken from the pustules of 

 cow pox and applied to the skin of human beings would inoculate them pro- 

 ducing a mild infection which immunized them against small pox. 



Scarlet Fever. Although streptococci are constantly associated with this 

 disease, the majority of the medical profession does not believe that they are 

 the specific etiological factor. The virus of scarlet fever is present in the blood 

 in the early days of the disease and is believed by many to also be present in the 

 desquamated epithelium. 



Yellow Fever. The virus of this disease is present in the blood of affected 

 persons as has been proven by withdrawing such blood and injecting it into 

 healthy persons, thereby inoculating them. This virus is never transferred 

 directly from man to man. Man is always infected through the bite of a mos- 

 quito. The mosquito in turn acquires the organism by feeding on the blood of 

 yellow fever patients. 



Measles. As shown by Anderson the virus measles is present in the nasal 

 secretions and the circulating blood prior to the development of the rash. 



Anderson's work has clearly shown that this virus is transmitted from man 

 to man by direct intimate contact during the period of coryza and before the 

 rash develops. 



There is much evidence to indicate that scarlet fever is probably transmitted 

 in a similar manner. 



