100 THE AMERICAN MONTHLY [May, 



favorable circumstances, double their numbers hourly, so that you can 

 judge for yourselves whether it is best to preserve infected animals, the 

 systems of which are the spheres of this extraordinary fecundity of 

 poison, or to obliterate the system, the poison, and the rapidly growing 

 danger at one blow. It is manifest that the limits naturally set to the 

 propagation and increase of one of these plague-bacteria are only set 

 by the number of animals that are susceptible to its attacks and within 

 its reach. The greater, therefore, our live-stock possessions of a genus 

 receptive of a given poison, and the more the material wealth of this 

 kind at stake, the more rapid is the spread of the infection and the 

 greater the national loss. 



It also follows, without saying it, that a specific plague-bacterium, 

 unknown on this continent for the centuries since its discovery, and 

 finally imported from abroad, should be stamped out remorselessly, and 

 at once, whatever the temporary inconvenience and outlay. We have 

 heard that the only way to root out thistles is to draw off the coat and 

 eradicate them one by one by sheer manual labor. But no amount of 

 labor nor effort which the individual man can apply can root out these 

 bacteridean xveeds that average only y-g-o¥"o °f an i ncn m length, that 

 can only be seen under the highest available powers of the microscope, 

 and then only after they have been deeply dyed with some bright pig- 

 ment. 



Following is a partial list of the disease-producing bacteria of the farm 

 animals, which give some idea of the extent of this great subject. This 

 is, however, only the beginning of the animal plagues caused by para- 

 sites. The fungi and animal parasites are responsible for a long list 

 beside. 



Disease-Producing Bacteria. 



ist. Micrococcus. — Round or ovoid cell. 



M. of cow-pox and horse-pox. 



M. of sheep-pox. 



M. of cystitis. 



M. of erysipelas. 



M. of ulcerative endocarditis. 



M. of osteo-myelitis. 



M. of lobular pneumonia (horse). 



M. of lung plague (cattle). 



M. of influenza. 



M. of suppuration. 



M. of septic wounds. 



M. of gangrenous wounds. 



M. of fowl cholera. 



M. of diphtheria. 



Diplococcus of swine plague. 



Sarcina of the stomach. 



Sarcina of the urine. 

 2d. Bacterium. — Short rod. 



B. of blue cream. 



B. of yellow cream. 



B. of red cream. 

 jd. Leptothrix. — Chain of very fine cells. 



L. of mouth and carious teeth. 



L. of abortion (cattle). 



