38 C.C. NATURAL HISTORY SOCIETV. 



Again, in 1865, when the French silk industry was seriously 

 threatened by the mysterious " spot disease," Pasteur discovered the 

 cause in a microbe, which attacked the eggs and bodies of the worms. ' 

 The diseased eggs were detected under the microscope, and des- 

 troyed, and so the disease was crushed out. 



In 1849, ^ Frenchman, Davaine, had observed a microbe. Bacillus 

 Anthraas, in the blood of cattle which had died of enteric fever, a 

 disease which was then very prevalent amongst the French herds, and 

 which is now such a terror to the African farmer. Later, Pasteur, 

 while experimenting on Fowl Cholera, made a startling discovery. 

 He cultivated the bacterium, that is to say preserved in such a liquid 

 that it could feed and grow, and found that if he kept it for some 

 time it was not nearly so virulent, so that when he injected some of 

 it into a healthy fowl, mstead of the animal dying, it merely became 

 slightly unwell and then got right again, and further to the astonish- 

 ment of the experimenter, gave complete protection to the animal 

 when what would have been a fatal dose of the poison was adminis- 

 tered. 



It had long been known from the experiments of Jenner that cow- 

 pox, an attenuated small-pox, gave as complete a protection against 

 the latter disease as an attack of small-pox itself, but for nearly a 

 hundred years this had remained an isolated fact, it was now by 

 Pasteur's work linked to other similar observations and extended by 

 that experimentor and his pupil Koch to Hydrophobia and Anthrax, 

 Since then disease after disease has been found to be caused by some 

 particular bacillus and its antidote has been found to be an injection 

 of the same bacillus in a less virulent form. 



The average microbe is some one-twenty-thousandth of an inch 

 long, and the forms of these minute organisms are very varied. They 

 are undoubtedly vegetable in their nature, they increase by splitting 

 into two parts, each part going on living, and also by forming little 

 round bodies called spores, which are very hard and difficult to kill, 

 some resisting even boiling water and the inlensest cold. The spores 

 of Anthrax will stand a temperature of 100 degs. Cent, for some time, 

 while the bacilli are killed by ten minutes boiling. Microbes increase 

 at an enormous rate, one observer states that seven in twenty drops 

 of water had multiplied to 495,000 in the course of two days. 



It is a curious thing that a microbe which is poisonous to one 

 animal is not necessarily so to another. Anthrax for example, is a 

 virulent poison to cattle, sheep, rabbits, guinea-pigs and mice, and has 



