380 THE AIR OF TOWNS. 



Perhaps one of the happiest and most fruitful results of the study of 

 this engrossing subject has been the antiseptic treatment of disease, 

 first introduced by Sir Joseph Lister. In speaking upon this subject, 

 the late Professor Tyndall said : 



Consider the woes which these wafted particles during historic 

 and prehistoric ages have inflicted upon mankind; consider the loss 

 of life in hospitals from putrefying wounds; consider the loss in places 

 where there are plenty of wounds, but no hospitals, and in the ages 

 before hospitals were anywhere founded; consider the slaughter which 

 has hitherto followed that of the battlefield, when these bacterial 

 destroyers are let loose, often producing a mortality far greater than 

 that of the battle itself; add to this the other conception that in times 

 of epidemic disease the selfsame floating matter has mingled with it 

 the special germs with j>roduce the epidemic, being thus enabled to 

 sow pestilence and death over nations and continents — consider all this 

 and you will come to the conclusion that all the havoc of war ten times 

 multiplied would be evanescent if compared with the ravages due to 

 atmospheric dust. 



If after disinfecting by killing the germs we can exclude the air, or 

 the dust of the air, the most putrescent substances may be kept indefi- 

 nitely without the slightest indication of putrefaction. Both Pasteur 

 and Tyndall have established this fact in the most convincing manner, 

 the former by allowing calcined air (that is, air passed through a red- 

 hot tube) to come in contact with a highly putrescible substance like 

 beef extract, the latter by giving the substance access to dust-free air 

 in a chamber similar to one shown in my last lecture, the purity of the 

 air being tested by a beam of light. I have referred to the relations 

 of dust to epidemic diseases in the paragraph quoted from Professor 

 Tyndall. This relationship is perhaps not quite so obvious as that 

 which has been found to exist between the germs of the air and festering 

 wounds. 



To discover this relation, we must again seek it in a research of Pas- 

 teur—one of the noblest services that any man has rendered to his 

 country. The outline of the story is briefly told. 1 



For fifteen years, a plague raged among the silkworms in the 

 silk-growing district which lies to the southeast of France. From 

 130,000,000 francs, which was the value of the silk produced in 1853, it 

 had dropped to 30,000,000 francs in 1862, and there was no sign of 

 abatement of the disease. 



In 1803 the French minister of agriculture offered a reward of £20,000 

 to anyone who should find a remedy. The district which suffered most 

 was Alais, the country of Pasteur's friend, the chemist Dumas, who 

 wrote to Pasteur, " I put a great price upon seeing you fix your atten- 

 tion on the question which interests my poor country. The misery 

 there surpasses all imagination." In June, 1865, Pasteur gave up his 

 post at Paris and with his wife left for Alais. The disease of the 



l A. fuller account may be found iu Tyudall's " Dust and Disease." 



