io8 Minnesota Plant Life. 



and this under such conditions of g'encral health that it is hoped 

 the patient may contract the disease, become acchmated 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 ]:)racticed in China. I'acciuatioii is a name ij;-iven 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 

 l)ody — a very different i)rocess 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, ])ro(luced 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 ff)0(l from the poisoned tissue. 'Phus is explained the 

 habit of the consuniplion-germ of making tubercles in llie lungs. 

 It was Koch's idea that he could. 1)\ means of his lymph. j)oison 

 the lung-tissues artificially, not enough to kill the i)atient. 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 infcriious and contagious diseases after they ha\-e begun 

 to develoi* in llie palit-'ul, is supplied by the process known as 



