94 THE DISEASES OF DOMESTIC ANIMALS. 



ganism, experience seems to justify us in assuming that much greater 

 quantities are necessary with regard to the so-called malarial diseases. 



Miasmas are not transportable in the sense of the infectious ele- 

 ments of purely contagious diseases. 



We can not acquire intermittent fever at any time or place, but 

 must be in localities where it is generated. 



In septic diseases, we have, fortunately, still another condition. 



The continued introduction of infectious material is necessary to 

 produce septicaemia ; for experience has taught us that if, by disin- 

 fection of the wound, we can shut off the supply, even though the 

 wound continues, we may prevent the general disease. We know, 

 further, that we can introduce, subcutaneously, no inconsiderable 

 amount of septic material into a rabbit, without causing fatal re- 

 sults ; but, if we continue the supply, the general disease, blood- 

 poisoning, follows. 



We do not know why it is that one individual of a given species 

 is susceptible to infection by a contagious disease, and another not ; 

 or why at one time an individual may become infected and at an- 

 other not ; or why at one time we may go to a locality where inter- 

 mittent fever or yellow fever prevails and not become diseased, while 

 at another time we may acquire either of them. 



In fact, when we come to the earnest study of the causes of con- 

 tagious infections, as well as malarial diseases, we become more and 

 more convinced that our ignorance far surpasses any knowledge that 

 we may possess. 



Dispersion of Bacteria, and their Entrance into the Anevial 



Organism. 



The deeper we seek to penetrate into the life and functions of 

 the bacteria, the more do we feel ourselves as lost wanderers upon 

 an unknown sea. We find very few known facts to cling to, as rocks 

 of refuge to the storm-tossed mariner. There are but few beacon- 

 lights along this coast. 



There are no more important questions in connection with bac- 

 terial life than as to the means by which they become separated and 

 dispersed from the original places of generation ; and, again, how 

 they enter from these into the animal organism. 



Notwithstanding our poverty of knowledge, we have still some 

 points of practical value at command to aid us on our way. 



We have all-sufiiciently established the non-gaseous nature of 

 the elements causing contagio-infectious diseases — a fact which will 

 become still more apparent as we pursue our studies. 



