MICROBIAL DISEASES OF MAN AND ANIMALS. 653 



Cowpox is characterized by eruptions which usually occur on the 

 skin of the teats and udder. The lymph 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 incubation 

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

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

 depends 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 typical skin erup- 

 tions, 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 and severe 

 pains in the muscles and joints. The fever during the attack shows a 

 characteristic curve. There is a sudden rise of and maintained tempera- 

 ture for several days. Then a remission and a second rise of tempera- 

 ture 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 contagious in the 

 ordinary sense but that it is transmitted through the bite of the mosquito 

 (Culex fatigans). No visible organism could be demonstrated in either 

 fresh or stained specimens of blood from patients affected with dengue 

 although such blood was capable of producing a typical attack of 

 dengue 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 or- 

 ganism of dengue fever is therefore probably of ultramicroscopic size. 



FOOT-AND-MOUTH DISEASE.* 



Foot-and-mouth disease is primarily a disease of cattle, though the 

 other domestic animals and man may be attacked. The disease is very 



* Prepared by M. Dorset. 



