390 FARMERS' INSTITUTES. 



CONTAGIOUS DISEASES— PLETJKO PNEUMONIA. 



DR. MANLY MILES, OF LANSING. 



At the Charlotte Institute Dr. Miles spoke on the above subject, and from 

 his remarks the following notes were taken. 



Oar knowledge with regard to the contagious diseases of our domestic 

 animals has very largely increased of recent years. 



We used to rely upon quarantine as a sufficient defense against them in all 

 cases, but now we often tind the most rigid quarantine of no avail. 



We have to call in science to our aid. Experience is a good foundation, 

 but science marks out the road for experience to follow. The two must go 

 hand in hand and be mutual helpers. Science sets up the guide boards and 

 practice finds ways and means of following. 



These sciences have aided as greatly in solving the why of success, and so 

 enables us to select the causes of success and avoid the causes of failure. 



The microscope has among scientific aids done as much for us as anyone 

 instrumentality; and this chiefly in the line of the study of microbes. 

 It is remarkable to what an extent this study of micro organisms is giving 

 light in what have been hitherto dark directions. One of the most familiar 

 forms of this germ life is seen in the common beer yeast. The fermentation 

 in beer and in the yeast of bread is caused by the multiplication of the yeast 

 plant. This appears on examination to be a mere cell which multiplies by 

 budding out new cells. These cells are of different forms in different por- 

 tions of the yeast. In high yeast the cells are nearly circular, and thrive 

 best near the surface of the fluid, while in the lower portions of the fluid a 

 more elongated form thrives best. In some cases yeast cells are very much 

 elongated — even four times as long as broad. 



Even in these low forms of life the law of the survival of the fittest pre- 

 vails with the same force as among higher beings. The individuals that are 

 best adapted to the circumstances in which they are, will live and multiply 

 and crowd out of existence those which are not so well fitted to their sur- 

 roundings. They are affected by temperature, by the density and quality of 

 the substance in which they are and in short, just as we are, by all the con- 

 ditions to which they are subject. 



Commercial yeast is made up largely of high and low forms with a little of 

 several other forms. In making bread if you give the conditions for high or 

 low forms they will grow, if for neither of them, then one or the other of the 

 various other forms will probably grow. These long forms multiply by divis- _ 

 ion with exceeding rapidity. It is estimated that if there were nothing to 

 check ttieir increase, a single individual, g-j^^-g-g-ii^ch in diameter, would by 

 reproduction fill the ocean solid one mile deep in five days. Some forms are 

 useful, others harmful. We could not live without some of them. Pasteur 

 found that acetic fermentation, lactic fermentation and butyric fermentation 

 are also due to similar growths. Some are similar in form but different in 

 action. Anthrax, a fatal disease, is caused by germs which multiply by fis- 

 sion and by spores, the latter being harder to kill than mature forms. Pas- 

 teur found that these are capable of a sort of attenuation by which a mild form 

 of disease could be given which would protect from severe types. So Pasteur 

 studied the silk worm disease and found a similar cause and a remedy. Tuber- 



