INFECTION. 89 



Reproduction by Spores. 



Until recently multiplication by fission was the only form of 

 bacterial reproduction admitted by naturalists. 



The formation of spores has been observed in bacillus subtilis 

 (Colin), bacillus anthracis (Koch), and in bacillus amylobacter by 

 another observer. 



In cultivation experiments made with hay-infusion we may see, 

 at a certain moment, in the homogeneous filaments of the bacilli, 

 very refractive corpuscles making their appearance. Each of these 

 corpuscles becomes a spore, oblong, or in the form of a short fila- 

 ment, highly refractive, and having well-defined outlines. We find 

 the spores arranged in a simple series in the filaments. So soon as 

 the formation of spores has terminated, the filaments can no longer 

 be distinguished, and one would say that the spores were com- 

 pletely free in the mucus ; but their linear arrangement shows that 

 they are produced in the interior of the filaments. These dissolve 

 slowly, and the spores, being reduced to a fine powder, settle to the 

 bottom of the liquid, where they may be found in great quantity. 



The germination of spores does not apparently follow in the 

 same medium ; but, if we remove them to a new cultivating fluid, 

 we may observe the spore to swell up and elongate, resembling a 

 "bacterium with a head. Soon the head, the most refractive portion 

 of the object, disappears, and the tube stretches into a short rod- 

 bacillus, commences to display motion, and becomes jointed by 

 transverse division. 



The Action of Bacteria, wrra Reference to Contagious and 



Virulent Diseases. 



One of the peculiarities of all life is the struggle for existence. 

 Both animal and vegetable life is encompassed by this fact. Indi- 

 viduals of the same kind and those of a different kind all live at the 

 expense of one another. Many perish in the conflict. 



Life is a constant struggle with death. Even the individual 

 cells of which the organs of our body are composed undergo this 

 constant struggle ; the stronger overcome the weaker. So it is 

 with disease. 



The germs of infectious diseases on entering the animal organism 

 at once begin a conflict with the elements of the same for nutritious 

 material. If the elements of our bodies are the stronger, they 

 finally overpower these disease-producing enemies, and we live ; if 

 the latter are the more powerful, we die. 



