Minnesota Plant Life. 109 



scrum therapy. In order to understand this it must l)e noticed 

 that the relation between l^acteria and an animal which they are 

 infesting is reciprocal. Jnst as tlicy poison the organism so do 

 certain compounds in the blood-serum poison tlicni. The sub- 

 stances generated in the blood and poisonous to bacteria are 

 known technically as anti-toxins. Now acclimatization to 

 germ diseases seems to be in part, at least, due to a develop- 

 ment of anti-toxins in the blood-serum — that is, in the watery 

 part of the blood in which the corpuscles are suspended. So if 

 a horse or other animal be acclimated to a disease — diphtheria, 

 for example, — and then the serum from such an animal l)e in- 

 jected into the veins of a patient suffering from the disease in 

 question, a supply of anti-toxins is put in a position where it can 

 poison the disease germs. This treatment, indeed, has been re- 

 ported as successful for diphtheria — so much so, that if proper 

 serum is quickly obtainable, even a malignant case, taken in its 

 early stages, can be combatted. A time may be expected when 

 anti-toxins will have been discovered for all of the dangerous 

 germ diseases wdiich kill annually so many hundreds of thou- 

 sands of the human race. Serum-therapy may be described as 

 a sudden acclimatization of the blood through the injection of 

 acclimated serum from another animal, and it is exactly com- 

 parable to the use of antidotes for ordinary cases of poisoning. 

 The antidote, however, is taken directly into the blood and not 

 into the stomach. 



Diseases of animals and plants. Not only are men subject 

 to a large number of bacterial diseases, but also domestic ani- 

 mals, birds, fish, tiny water insects and crustaceans, or even 

 plants — and among the latter should not be omitted the bacteria 

 themselves, for it is well-known that some varieties are so in- 

 imical to others that they may produce a growth wdiich will de- 

 stroy the original colony. Plant bacterial diseases, such as pear- 

 blight, potato-scab, cucumber-rot and carnation-blight are not 

 uncommon in Minnesota and considerable damage results from 

 their activity. No highly effective methods of combatting them 

 have as yet been devised. Plant-quarantine against infected 

 plants, plant-hygiene and sanitation and the selection of resist- 

 ant varieties represent about the extent of modern treatment. 



Bacteria of putrifaction. Among the ferment-producing bac- 

 teria, those which convert organic substances into compounds 



