34 JOHN J. STEVENSON 



But the scab is no longer a frightful burden in California; the 

 potato bug is now only an annoyance, and the introduction 

 of lady birds swept aphides from the Sandwich islands. The 

 g>7)sy moth, believed for more than a hundred years to be a 

 special judgment, is no longer thought of as more than a very 

 expensive nuisance. The curculio, the locust, the weevil, 

 the chinch bug, and others have been subjected to detailed 

 investigation. In almost all cases methods have been devised 

 whereby the ravages have been diminished. Even the borers, 

 which endangered some of the most important timber species, 

 are now understood, and the possibility of their extermina- 

 tion has been changed into probability. 



Having begun with the infinitely great, we may close 

 this summary with a reference to the infinitely small. The 

 study of fermentation processes was attractive to chemists 

 and naturalists, each claiming ownership of the agencies. 

 Pasteur, with a patience almost incredible, revised the work 

 of his predecessors and supplemented it with original investi- 

 gations, proving that a very great part of the changes in 

 organic substances exposed to the atmosphere are due pri- 

 marily to the influence of low animals or plants, whose germs 

 exist in the atmosphere. 



One may doubt whether Pasteur had any conception of 

 the possibilities hidden in his determination of the matters at 

 issue. The canning of meats and vegetables is no longer 

 attended with uncertainty, and scurvy is no longer the bane 

 of explorers ; pork, which has supplied material for the building 

 of railroads, the digging of canals, the construction of ships, 

 can be eaten without fear. Flavorless butter can be rendered 

 delicious by the introduction of the proper bacteria; steriHzed 

 milk saves the Hves of many children; some of the most de- 

 structive plagues are understood and the antidotes are pre- 

 pared by the culture of antagonistic germs; antiseptic treat- 

 ment has robbed surgery of half its terrors, and has rendered 

 almost commonplace operations which, less than two decades 

 ago, were regarded as justifiable only as a last resort. The 

 practice of medicine has been advanced by outgrowths of 

 Pasteur's work almost as much as it was by Liebig's chemical 

 investigations more than half a century ago. 



