INFECTION. 95 



In all strictly contagions diseases, yon Avill remember, the ele- 

 ments of infection are always generated witliin the diseased organ- 

 ism, and pass off with the excretions, or are attached to them. 



In miasmas they are always generated ontside of any animal 

 organism. This distinction mnst never be lost sight of. 



It is trne we have infections diseases, in which, originally, the 

 etiological elements are generated ontside the organism, and which 

 have a certain degree of contagiousness by means of their excre- 

 tions. This is tiie group of infcctio-contagious diseases of which 

 febris tlava and anthrax are examples. 



AVherever infectious germs are produced, their generation is 

 based upon the 2>i'esence of moisture, either as a watery fluid or 

 some substance containing moisture sufficient to the purpose. 



We find no difficulty in comprehending the dispersion of infec- 

 tious elements when they are still contained within or upon the ma- 

 terials where they have been generated, that is, by means of streams, 

 or of solids or fluids impregnated with them. Distribution or disper- 

 sion of infectious stuff in this way is by no means the rule ; in fact, 

 it is seldom that it takes place to any distance, unless artificial means 

 come into play. Glanders, variola, and syphilis can only be ac- 

 quired by direct contact with an infected organism, or with a vehicle 

 which has been polluted with the specific elements of either of 

 these diseases. 



Only the infectious elements — inficientla — of purely contagious 

 diseases are capable of any wide dispersion, and this can only take 

 place through the moving of diseased individuals or the transport 

 of derivatives from the same — clothing, excretions, hides, horns, 

 hair, etc. — or through accidental substances which may have become 

 impregnated with excretions from them. Elements of infection 

 can only be dispersed in two ways : 



1. By means of water or fluids, or moist substances containing 

 them. 



2. By the air, or in some desiccated vehicle or condition. 

 Infectious elements do not long retain their original condition 



and activity in water. The nature of the nutriment found in such 

 media exerts a corresponding influence upon the nature and activi- 

 ties of genns. Metamorphosis into non-malignant forms is fre- 

 quently said to take place. 



In jiure spring or rain water they soon demonstrate changes for 

 ■want of sufficiency of nutriment. They retain their specific char- 

 acteristics longest in those media in which they are originally gen- 

 erated. 



