CHAPTEE IV. 



METHODS OF SPREAD OF DISEASE— DISINFECTION- 

 IMMUNITY. 



The methods of spread of infection — Measures to prevent the spread 

 of diseases — Vaccination — Quarantine — Notification — Practical dis- 

 infection — Disinfection of rooms^ — Disinfection by sulphur, chlorine, 

 heat, steam, etc. — Immunity and susceptibility — Hypothesis of 

 immunity — The exhaustion or pabulum, antidote or retention, and 

 acquired tolerance hypotheses — Antitoxin treatments — Putrefaction 

 and oxidation. 



The Methods of Spread of Infection. — The principal methods 

 of infection are : 



1. Pi^lmonary infection, the bacilli or spores being 

 inspired. 



2. Intestinal infection, the organisms being swallowed 

 with food, water, or dust. 



3. Inoculation through a wounded or un wounded surface 

 of the skin or mucous surface. 



4. Infection by contagion, fomites, etc., in which the 

 manner of entrance of the virus into the body is not pre- 

 cisely understood. 



We will now proceed to briefly consider to which of the 

 above classes some of the various diseases belong : 



Actinomycosis. —Very rare in man, usually caused by the 

 chewing of ears of cereals infested with the fungus. Possibly 

 infection is also by inspiration. Two or three cases are on 

 record where infection has been conveyed from animals to 

 man. Class 3. 



