CHAPTER II. 



COT^TAGIOUS AND EPIZOOTIC DISEASES. 



Their importance and classification. Germs the cause of plagues. Purelj 

 contagious diseases preventible. Propagation of disease-germs outside the 

 animal body. General characters of micro-organisms causing disease. Form 

 inconstant in different media. Viability of bacterium and spore. What 

 they eat, breathe, and excrete. Alkaloids and ferments. Antagonism be- 

 tween bacteria and blood-globules and tissue-nuclei. Relative susceptibility 

 of blood, lymph, and solid organ. Effects of acid and alkaline media, of 

 light, electricity, heat, cold. Fecundity of bacteria. List of bacteria pro- 

 ducing animal diseases. Rendering animals insusceptible to a plague. 

 Direct cause of acquired immunity. Exhaustion theory. Antidotal theory. 

 Condensation theory. Vital resistance. Immunity by good hygiene ; by 

 tonics and anti-ferments ; by a first attack ; by inducing a mild type of the 

 plague ; by inoculation of <i closely related disease ; by inoculation of a 

 minimum amount of virus ; by arrest of the disease while still local — anti- 

 septic ; by inoculation in an unimportant organ ; by inoculation in the veins ; 

 by inoculation with germs weakened by passing through another genus of ani- 

 mal ; by inoculation with germs weakened by cultivation in special media ; 

 by inoculation with germs grown for long in free contact with air ; by 

 inoculation with germs weakened by condensed oxygen ; by inoculation with 

 germs weakened by long rest in free air ; by inoculation with the sterilized 

 products of germs. Advantages of the use of sterilized virus. Drawbacks. 

 Limitation of protection by sterilized products. Radical extinction of plagues. 

 Measures for extinction of a prevailing plague. To exclude an animal 

 plague from a country. Disinfection. 



These are among the most important of the whole range 

 of diseases of animals, being the most destructive to the 

 animals themselves and in many eases to man, and being at 

 the same time, as a rule, preventible by a rigid adherence 

 to sanitary laws. Of their devastations we have the most 

 appalling accounts in the records of antiquity as well as ir 



