io8 Minnesota Plant Lift. 



and this under such conditions of general health that it is hoped 

 the patient may contract the disease, become acclimated to it, 

 so to speak, and thus avoid it at a time when his physical state 

 might not be so favorable to withstand it. In the old days this 

 means was adopted to diminish the mortality from smallpox and 

 is still practiced in China. Vaccination is a jiame given to the 

 injection, into the body, of a mild form of disease-bacteria; 

 because when the body thus becomes acclimated it is more re- 

 sistent to the virulent form. The remarkable discovery of Jen- 

 ner that cow-pox was a mild form of smallpox, and that after 

 vaccination had "taken," as the saying is, one would not then 

 easily contract the malignant disease, was the precursor of other 

 types of vaccination, such as those of Pasteur, who vaccinated 

 successfully with mild anthrax and mild hydrophobia, thus ren- 

 dering the vaccinated individual immune to the more virulent 

 types of these maladies. 



Koch's lymph. Quite a different attempt to control such a 

 disease as consumption was that of Koch, whose famous lymph, 

 a few years ago, was much exploited in newspapers and peri- 

 odicals. It had been known for some time that the bacteria of 

 consumption could be cultivated outside the human body upon 

 a variety of substances such, for example, as beef-broth jelly. 

 Cultures of the consumption germ were made in this way by 

 Koch, and by means of glycerine an extract of their poison was 

 prepared. The extract of poison was then injected into the 

 body a very different process from vaccination, because in that 

 case the germs themselves are placed in the body of the patient. 

 It had been observed that the consumption bacteria, like other 

 sorts, produced around the patches where they grew, excreta to 

 such an extent that they poisoned the tissues of the body and 

 limited the growth of their own colonies, which were unable to 

 absorb food from the poisoned tissue. Thus is explained the 

 habit of the consumption-germ of making tubercles in the lungs. 

 It was Koch's idea that he could, by means of his lymph, poison 

 the lung-tissues artificially, not enough to kill the patient, but 

 enough to prevent the bacteria from developing. In this effort 

 he was not entirely successful. 



Serum therapy. Another and more hopeful method of com- 

 batting infectious and contagious diseases after they have begun 

 to develop in the patient, is supplied by the process known as 



