268 BOARD OF AGRICULTURE. 



like short blunted rods. It was found by further experi- 

 ment that these germs could also be cultivated, in a proper 

 medium, outside of the animal body, and that after carrying 

 them through a number of generations, in a way similar to 

 the one used to reproduce the bacteria of anthrax, that we 

 have just described, they were still as potent to produce 

 consumption, when injected into the bodies of rabbits, as those 

 taken directly from the body of the person or animal suffering 

 with the disease. It was also demonstrated that these culti- 

 vated germs could 1)c communicated to animals through the 

 medium of the air by the following experiment. After con- 

 fining a numlier of animals in a convenient room, it was 

 arrans^ed so that all of the air these animals breathed must 

 first pass over material filled with these germs. In a few 

 weeks all of these animals sickened and died, while other 

 animals confined and fed in the same way, except that they 

 were supplied with uncontaminated air, remained healthy. 



Now, experiments like those just described, and sipiilar 

 ones, have been made, — not only in the study of anthrax and 

 consumption, but also in the study of nearly, if not all, of 

 the contagious diseases, such as cholera, typhoid fever, the 

 pleuro-pneumonia of cattle, the swine plague, etc., — not 

 by a single observer, but by Pasteur, Koch, Sternberg, 

 and hundreds of others, who have either carried on original 

 experiments, or else have imitated those of these three great 

 masters I have named, and all have come to the same general 

 conclusion, namely, that the contagious diseases are pro- 

 duced by a minute form of vegetable life, called bacteria, 

 finding lodgment in some part of the human body, and there 

 reproducing themselves, or in other words, growing, — dif- 

 ferent species of these bacteria [)roducing difi'erent forms of 

 contagious diseases. Further, thtit contagious diseases are 

 communicated from the sick to the well by the germs 

 causing the disease being conveyed' in one way or another 

 from the sick to the well, eacli person infected and develop- 

 ing the disease making a new focus or starting point from 

 which it may be communicated to others. 



I will now show you upon the screen a few of the difi'erent 

 species of these disease-producing bacteria that have been 



