QUESTIONS 51 



excellence carriers of the infection. The most important examples 

 of such intermediary hosts are: 



Mosquitoes, carrying malaria from man to man, or from birds to 

 birds. 



Tsetse-flies, carrying trypanosomiasis from animal to animal or 

 to man. 



Fleas and lice, carrying bubonic plague from man to man or 

 animal to animal, or from animals to man. 



Ticks, carrying Texas fever from cattle to cattle. 



Bed-bugs, carrying relapsing fever from man to man. 



Summary. It has now been shown that the routes of entrance 

 into the bodies of susceptible animals for pathogenic bacteria are 

 the following: 



1. Through wounds of the skin or mucous membranes. 



2. By inhalation. 



3. By ingestion with food or drink. 



4. By intimate contact, particularly by sexual intercourse. 



5. Through the placenta! circulation. 



Excretion of Pathogenic Bacteria. This takes place in different 

 ways according to the place of entrance and the localization of the 

 bacteria. An infected wound may be open from the start and dis- 

 charge, and disseminate the infecting bacteria; or an abscess may 

 have been formed when the excretion of the bacteria will only take 

 place after the abscess has broken and established direct or indirect 

 communication with the outside world. In tubercular infections, 

 glanders, pneumonia, influenza, and strangles, the specific pathogenic 

 bacteria are discharged through the natural communicating operi- 

 ings of the upper respiratory tract, or the pathologic products of these 

 diseases may be swallowed and the bacteria discharged with the 

 feces. In anthrax many of the bacteria are discharged with the feces, 

 the urine, and also the bloody, foamy fluid flowing from the nostrils. 

 In typhoid fever, Asiatic cholera, fowl cholera, bacillary dysentery, 

 swine erysipelas, the disease producers are voided in enormous 

 numbers with the feces. The organisms causing infectious abortion 

 and infectious vaginitis in cows are discharged with the vaginal 

 secretion and also to some extent with the urine; the latter contains 

 innumerable specific bacteria in bacillary pyelonephritis in cattle. 



QUESTIONS. 



1. Name some facultative parasites which are extensively found in the 

 outside world and only occasionally as pathogenic parasites. 



2. Name some obligate parasitic bacteria which are only found where they 

 have been spread by infected persons or animals. 



3. Where are the anthrax bacillus and the ray-fungus found so that they 

 may spread the disease with fodder? 



4. What are the portals of entrance through which pathogenic bacteria may 

 invade the body of a susceptible animal? 



