336 AGRICULTURAL BACTERIOLOGY. 



be worked out among men. He may, by breeding, produce 

 animals with some valuable feature most extremely developed ; 

 but in so doing he must remember that he is producing ab- 

 normal animals that are likely to have little resisting power 

 against disease. He may feed them with stimulating food 

 and force them in lines which suit him ; but he must bear in 

 mind that there is a limit to the possibilities, since all of these 

 methods of treatment lead to abnormal conditions and greater 

 liability to disease. 



Nothing is more important than that the agricultural com- 

 munity should fully appreciate that resistance to infectious 

 diseases on the part of domestic animals is in large measure an 

 individual matter, depending upon the most vigorous health 

 and the most normal conditions of life. The adoption of pre- 

 cautions for preventing the distribution of the disease germs is 

 doubtless a matter of very great significance, but of more sig- 

 nificance still is the endeavor so to modify the conditions of 

 life as to increase their resisting power against these bacteria. 

 In every case, doubtless, the plan adopted will be by the way 

 of compromise, and will be such as to give the greatest amount 

 of physical vigor consistent with the ends which the farmer has 

 in view in his use of the animals. To turn them out into the 

 fields with no attempt to produce special types, and with no 

 high feeding would doubtless produce a vigorous breed, but it 

 would not produce milk. 



It does not fall within the scope of this work to consider 

 at length the various animal diseases which are produced by 

 the growth of bacteria in the living tissues. This subject be- 

 longs to the veterinarian rather than to the agriculturist. 

 There are a few of these diseases, however, around which a 

 monumental mass of bacteriological information has been col- 

 lected, and two of these, at least, are of special significance to 

 agriculture ; one because of its scientific and historical interest, 

 and the other because of its extremely practical bearing upon 



