308 APPENDIX. 



uot be consumed by the animal kingdom as now organized. The 

 first function of the bacterium is to disintegrate the remains of de- 

 funct life and resolve it into its elements for the assimilation, growth, 

 and sustenance of the next generation. After the bacterium has per- 

 formed its function, nature's next obligation is to get rid of it This 

 she effects mainly by means of sunlight The direct rays of the 

 sun are mortal to bacteria. As the bacterium progressively reduces 

 to their elements more and more of the foreign matters suspended 

 in water, it becomes clearer ; turbidity disappears ; the sun's rays 

 penetrate it deeper and deeper. Under their fatal influence the bac- 

 teria, their work done, perish. 



But nature supplements the sun's rays by another agency, the 

 very small creatures called animalculte. Many persons have seen 

 the image of these projected on a screen by the magic lantern. 

 They dart about freely in their drop of water ; they are of bizarre 

 and fantastic shapes; they are absolutely harmless taken into the 

 animal system, where they perish, like the oyster, under the diges- 

 tive process. They are, in fact, the necessary friends of the animal 

 kingdom. They cause the bacterium's destruction in places which 

 the direct solar ray is unable to reach. But for their presence bac- 

 teria would multiply indefinitely in such protected spots, although 

 they no longer have a place to serve in the necessary economy of 

 nature. Hence she gets rid of them, and the animalcula is her 

 adopted agent or means. 



Certain species of these micro-organisms, their number compara- 

 tively small, are pathogenic or injurious to man and most other an- 

 imals. Of these the commonest are those that cause consumption 

 and typhoid fever. The first is a typical example of the kind that 

 are disseminated dry by the air ; the second the kind introduced into 

 the animal system by food and drink. Each must find the system 

 in a condition favorable for its propagation, and each has preferred 

 tissues in which to work. For example, the comma bacillus of 

 cholera is able to operate only upon the intestines. It is harmless 

 if inhaled. The tubercle bacillus finds its most favorable field in 

 the lung tissue, to reach which it must be inhaled. It is usually 

 harmless when swallowed, but it is possible for it to cause tubercu- 

 lar degeneration in tissues other than the lungs if their condition be 

 favorable. All saliva is at all times charged with myriads of bacilli. 

 Among the many species the tubercle bacillus is nearly always 

 present Yet, taken into the healthy digestive system, it is harm- 

 less, as are all the rest * * * . New York Evening Sun. 



