14 MICROBES AND THE MICROBE -KILLER. 



How is this ? In the first place, certain germs must, 

 as I have already shown, have certain suitable condi- 

 tions in which to increase and flourish ; and although 

 they may be produced in abundance in such locations as 

 those described, yet the plants that grow in the same 

 spots are proof against them, they are not suited to 

 their development, and, in fact, they grow in spite of 

 them. That germs are produced in such places every 

 victim of malaria can testify. 



But this calls for another observation. Plants are 

 adapted to the conditions that surround them, and, con- 

 versely, the climate of any locality has vegetable growth 

 adapted to it. High latitudes and high elevations are 

 the homes of the pines and firs, while more temperate 

 regions give us the olive and the oak, and in the tropics 

 the palms and all the grandest development of endo- 

 genous vegetation most abound. This is nothing more 

 nor less than a law arising out of the temperature and the 

 formation of the earth itself ; nevertheless it is every- 

 where evident that Nature leaves nothing unoccupied, 

 so that when the conditions are such that one form of life 

 cannot continue, we find another especially adapted to it. 



These, however, are exceptions in the vegetable world ; 

 but similar exceptions are to be found in the animal 

 creation. Life that flourishes in the tropics would perish 

 in Labrador, and the seal of Alaska would soon disap- 

 pear if removed to the waters of the Amazon. Animal 

 life is also to be met with under exactly the same condi- 

 tions as those in which we find the flowers that grow 

 apart from light and air in the dim recesses of the 

 woods. But this only proves the rule. The highest 

 and most complete forms of vegetation exist only under 

 the requirements given, and man, as the highest form 

 of animal life, requires the same. Like the oak and the 

 elm, he needs light, air, and a more or less equable tem- 

 perature. He does not flourish where the mushroom 

 and the snail are most at home. The gas that kills a 

 rose will destroy an animal. You may drown the one 

 Almost as readily as the other. Both succumb alike to 



