22 
stroyed by it, while others are similarly sensitive to sunlight, and 
again certain temperatures are fatal to certain species. 
bea or wih this subject, and constituting one of the 
ts of Hs iene, is that of methods of dis- 
o degr 
temporarily check their activity, while a degree of heat, cae 
secured by ordinary methods, and definitely fixed for each species, 
is fatal 
By far the most important precaution in our power is the pres- 
ervation of good general health and a high state of vitality. The 
foreign germs are never left by our body-cells to make an uncon- 
tested invasion. The battles between our cells and the foreigners 
have been actually photographed, showing defeat now upon one 
de, then upon the other. Manifestly, increased vitality means 
ort 
stricken by disease or re: ecome so if exposed, _ all 
do to avoid infection, or if infected, to pr eac 
cess in answering this question has been only aay ae 
yet this measure of success ean perhaps, the most remark 
able of all achievements in applied science. 
e present, we are pisceally without mineral or vege- 
oa 
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botanist, is solved by natural forces working within us. @ ex- 
istence of such a power is proven by the fact that we recover 
from these diseases, even after bette weakened by them, and al- 
though we were unable to resist them at first, when we were 
