Contagious and Epizootic Diseases. 35 



are either too mild to warrant such measures, or too easily 

 spread to be satisfactorily controlled by them. 



GEEMS THE CAUSE OF PLAGUES. 



Since the above was written the demonstration of the es- 

 sential causes of a number of these plagues in microscopical 

 vegetable ferments (microphytes) lias practically opened a 

 new field in pathology, prevention, and treatment. When a 

 plague is found to be due to seed sown in a susceptible 

 animal system, such seed being not a product of the 

 animal body, but derived from a different kingdom (the 

 Vegetable), and introduced from without the economy, it 

 follows that every case of such disease implies that the body 

 of the animal victim has been seeded for that particular 

 crop as a field is for wheat, barley, or rye, and in both cases 

 alike the seed sown has come from a preceding crop and 

 a preceding sowing. The parallel may be put thus : No 

 seed = no wheat; no germ = no plague. 



PURELY CONTAGIOUS DISEASES PEEVENTIBLE Wmi OEETAINTY. 



The moment we apprehend the fact that a particular 

 plague is essentially dependent for its existence on a specific 

 germ, we are compelled to the conclusion that it is quite 

 possible to prevent the spread of such a disease and to ex- 

 tirpate it from a country in which it has already gained a 

 foothold. If at a given date all English sparrows on the 

 American continent were destroyed, we would be rid of the 

 race until specimens were again imported. So with a plague 

 caused by a vegetable germ ; let all plague-stricken animals 

 and all the living disease-germs be destroyed, and the plague 

 would be certainly abolished. Ordinary hygiene makes no 

 such radical extinction of a plague. Clean, airy, wholesome 

 surroundings retard the progress of a plague and favor the 

 production of a milder type of the malady, but they allow 

 the preservation of the germ, ready to resume all its pristine 



