RESISTANCE AGAINST MICROORGANISMS 2777 
and of their resisting power against disease. It is the active, 
vigorous cow, which produces, perhaps, but little milk and is not 
carefully housed by the farmer that has the power of resisting 
disease. In short, the prevalence and the increase of some of 
the diseases of domestic animals must be attributed, in no in- 
considerable measure, to the introduction into our herds of con- 
ditions of life which lessen their resisting power, and not wholly 
to the increasing chances of contagion due to close contact of 
animal with animal. That the latter phenomenon is also a 
factor is, of course, evident. 
The conditions of life among domestic animals are, to a very 
large degree, under immediate and perfect control. We can regu- 
late the amount of outdoor life they have, their activity, their food, 
their drink, and many other factors upon which their physical 
vigor depends. We may keep the cow housed so that she has 
little air; we may give her highly stimulating food with practically 
no chance to use her muscles; or we can make quite a different ani- 
mal of her by changing her life and food. Wecan control the con- 
ditions of life among animals far better than we can, or will, those 
of our own life. In the conditions of civilized life each individual 
demands his personal freedom in regard to matters regulating his 
own affairs, and he absolutely refuses to be guided by rules and 
regulations, even though he may know them to be for his best phys- 
ical good. No matter how good rules for living our physiologists 
may make, they cannot force people to adopt them. But the 
farmer has absolute control over the life conditions of his stock. 
He can regulate their life as suits him, and he can, if he will, work 
out among cattle the problem of health and disease as it cannot 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 abnormal 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 pos- 
