72 



filtered through a Chamberland B filter for two hours under a pres- 

 sure of 29 inches of mercury, the filtrate was infective to a horse 

 into which it was injected. After an incubation of three days and 

 a clinical course of six days the horse died. 



Exudative typhus of chickens. — Magiora and Valenti a made 

 experiments with the emulsions of the blood, lungs, liver, spleen, 

 kidneys, and heart. They used the Berkefeld filter and Chamberland 

 F. Dilutions were made with 40 and 60 parts of physiological salt 

 solution and a pressure of 1£ atmospheres was employed. 



Bacteriological examination of the filtrate proved negative, but 

 chickens injected with 5 cc. of the filtrate died in about two days, 

 presenting the same clinical and pathological picture as the naturally 

 infected ones. 



Another set of chickens injected with the blood of the ones which 

 had received the filtrate developed typical symptoms and post-mortem 

 changes of the disease. 



An exposure of five minutes at 65° C. sterilizes the virus. 



These investigators found that the filtrates had very much less 

 virulence than the unaltered blood. Four cubic centimeters were 

 found to represent the minimum fatal dose of a filtrate from a mix- 

 ture of blood and water in the proportion of 1 : 160, whereas 4 cc. 

 represented the minimum fatal dose of an unfiltered mixture of 

 blood and water in the proportion of 1 : 1,500,000. 



It is interesting to note how the filtration experiments cleared up 

 an error which former students had made in regard to the loss of vir- 

 ulence in pure cultures of organisms which they had isolated in this 

 disease. They had found a cocco bacillus in the internal organs. The 

 culture tubes inoculated from the body fluids showed growths of this 

 organism. Inoculations into chickens from colonies on the first set 

 of cultures caused the disease, but subcultures from the first set of 

 cultures were not virulent. Into the first set of cultures there had 

 evidently been carried some of the invisible virus along with the 

 cocco bacillus. 



Mosaic disease of the tobacco leaf. — Beijerinck 6 pressed the sap 

 out of diseased plants and passed it through very thick porcelain 

 filters, and the filtrate was free from bacteria, but virulent for the 

 tobacco leaf. 



Epithelioma contagiosum of fowls.— -It was found by Marx and 

 Sticker e that the infective agent suspended in sodium chlorid solution 

 passed through a Berkefeld filter, but not through a porcelain filter. 

 The filtrate gave no growth on media; it was carried through a series 



a Magiora and Valenti : Ueber eine seuche von exsudativen typhus bei hiihnern. 

 Zeit. fur hyg. und infekkr., vol. 42, 1903, p. 198. 

 » Centrbl. fur bakt, Abt. 2. bd. 5. 1S99. p. 27. 

 "Deut. med. wochenschr., bd. 28, 1902, p. S92. 



