8o6 MICROBIOLOGY OF DISEASES OF MAN AND DOMESTIC ANIMALS 



bodies iii collodion capsules in the peritoneal cavities of experimental 

 animals. According to some investigators the virus has been passed 

 through a Chamberland filter. The failure to discover the causative 

 factor, according to the present methods, may be due to the inabiUty 

 of microbiologists to cultivate or stain the specific agent. ' 



CowpOx is characterized by eruptions which usually occur on the 

 skin of the teats and udder. The material contained in these pustules 

 is transferred to other animals by the hands of the milker and through 

 other possible means of dissemination. The chief channel of infection 

 appears to be through an abrasion in the skin. The period of incuba- 

 tion of cowpox is about two days. The virus possesses relatively weak 

 resistance ,to heat, Hght and chemicals. The control of the disease 

 depends chiefly upon precautions relative to the transmission of the 

 virus on the hands of the milker from infected to healthy cows. 



Horsepox may be diagnosed by the appearance of the characteristic 

 pustules usually upon the skin, nasal mucosa and buccal membrane. 



Sheeppox is characterized by the presence of the tj^jical skin 

 eruptions, following a rise of temperature. 



Dengue* 



This disease (break-bone fever) of man occurs in all parts of the 

 world. It is characterized by a sudden attack, intense prostration 

 arid severe pains in the muscles and joints. The fever during the attack 

 shows a characteristic curve. There is a sudden rise of and main- 

 tained temperature for several days. Then a remission and a second 

 rise of temperature which is less than the first. 



Our knowledge of the cause of this disease rests chiefly upon 

 researches of Ashburn and Craig (The Journ. of Infectious Diseases, 

 Vol. X, p. 440, 1907). These authors conclude that dengue is not con- 

 tagious in the ordinary sense but that it is transmitted through the bite 

 of the mosquito (Culex fatigans). No visible organism could be 

 dernonstrated in either fresh or stained specimens of blood from 

 patients affected with dengue although such blood was capable of pro- 

 ducing a t3^ical attack of dehgue when inoculated intravenously into 

 healthy men. The authors likewise show that blood from a case of 

 dengue retained its infectiveness after passage through a filter made of 

 diatomaceous earth. The organism of dengue fever is therefore 

 probably of ultramicroscopic size. * 



• Prepared by M. Dorset. 



