DISEASES PRODUCED BY ULTRA-MICROSCOPIC ORGANISMS 485 



temperature of 58. It will withstand drying for several months, 

 and liquids maintain their infectivity for months, even when decay- 

 ing. 



Pathogenesis. The virulent blood or blood-serum will infect 

 another animal upon subcutaneous injections of small quantities. 

 The incubation period after injection varies from five to nine days, 

 or even more. The initial symptom is a fever. The disease is 

 more apt to be acute when the organism is introduced by injec- 

 tions than by ingestion. The disease may be characterized as an 

 acute or chronic anemia which has the appearance of a septicemia 

 in which there is a great destruction of blood-elements. The 

 anatomical findings are characteristic. Mack, in his work on 

 cases in Nevada, notes profound cardiac and respiratory disturb- 

 ances. There is a progressive destruction of the red blood-cells, 

 parenchymatous degeneration of the kidneys and liver, and ex- 

 tensive changes in the vascular system. The spleen is engorged 

 and frequently degenerated, and the bone-marrow undergoes pro- 

 found degeneration. 



Immunity. Xo method of immunization has been developed. 



Transmission. European writers are of the opinion that in- 

 fection arises through the ingestion of food soiled by excretions 

 of infected animals. The mode of dissemination has not been 

 satisfactorily established. 



Virus of Dog Distemper 



Disease Produced. Dog distemper, Hundstaupe. 



Bacteria belonging to several different groups, particularly 

 to the colon-typhoid and to the hemorrhagic septicemia, have 

 been described as the cause of dog distemper. Carre, in 1905, 

 attributed the cause to a filterable virus. 



Distribution. Europe and America, probably in other parts 

 of the world. 



Nature of the Virus. Little is known of the virus beyond the 

 fact that it can be passed through a porcelain filter. It has not 

 been cultivated and is probably ultramicroscopic. 



Pathogenesis. The disease is a highly fatal, acute infection 

 of young carnivorous animals, characterized by an acute catarrh 

 of the mucous membrane, and frequently a catarrhal pneumonia. 



