BACTERIA IN THE INDUSTRIES 203 



characteristic changes in milk to which preservatives have been added ; in 

 fact, the failure to produce fermentation is an indication that preservatives 

 are present. 



5. MICROBIC PEST EXTERMINATORS 



Attempts have been made from time to time to exterminate certain 

 animal pests by inoculating them with some fatal contagious disease of 

 microbic origin. Experiments along this line have been carried on for 

 some time, ever since the causative relationship of microbes and disease 

 was fully established; but it is only within recent years that extensive 

 practical application was made of the use of a few microbic pest extermina- 

 tors. One of the first to be used with some success was the chintz-bug 

 exterminator. The chintz-bug (Blissus leucopteris, also called chinch-bug 

 chink-bug) was a very destructive corn (Zea mays) pest of the Central 

 States (Illinois, Kansas, Nebraska, Iowa) , causing great damage to crops 

 during certain very dry seasons. Extensive experiments carried on at 

 the University of Illinois and also at the University of Minnesota (Depart- 

 ments of Agriculture) led to the discovery of a microbic disease of this pest 

 which was quickly fatal and which spread very rapidly. The insects, in 

 cages, were inoculated with pure cultures of the pathogenic microbes, and 

 insects in the diseased condition were sent to the farmers with instructions 

 how to scatter them through an infested corn-field. The results were in 

 some instances very satisfactory, and again without appreciable effects. 

 The trouble in the use of this exterminator lay in the fact that the climatic 

 conditions (rainy, damp weather) essential to the spreading of the disease 

 did not generally prevail, and as soon as the climatic conditions were 

 favorable inoculation became unnecessary, as the disease developed 

 without artificial aid and effectuallv checked further ravages. 



Rabbits are one of the very annoying field pests of Australia, and at- 

 tempts have been made to exterminate them by means of pure cultures of 

 microbes capable of developing a fatal infectious disease among these 

 animals, but the results were quite unsatisfactory. 



More recently there have been placed on the market quite an array of 

 mice and rat exterminators of microbic origin under various trade names 

 as ratin, rat virus, azoa, rattite, Danysz virus and mouratus. These pre- 

 parations consist of pure cultures of bacilli pathogenic to rats and mice, 

 as the Bacillus murisepticus and Bacillus typhimurium, mixed with some 

 inert base, as corn-meal, oat-meal, etc., forming a coarse powder. Some 

 preparations are in liquid form. They are used by mixing the powder or 

 liquid with moist corn-meal or other food material relished by these 

 animals, and spreading it near their haunts and runs. Fortunately, 

 these substances are harmless to man and animals other than mice and 



