TUDES SUR LA MALADIE DES VERS A SOIE 751 



[LA ROYAL SOCIETY OK LONDON 



DCERNE A PASTEUR LA MDAILLE DE COPLEY 



POUR SES RECHERCBES SUR LA FERMENTATION ET LA PBRINE] () 



The Copley Medal has been awarded to Prof. Louis Pasteur, one of ou r 

 Foreign Members, for his researches on Fermentation and on Pebfine . 



Prof. Pasteurs researches on fermentation consist essentially of two 

 parts : tlie first part, in which he enters exhaustively into the examination 

 of the products formed in tins process; and the second, in which he takes 

 up the question of the cause of fermentation. 



Previous observers had noticed the production, in solutions of sugar 

 which had been fermentetl, of su 1 (stances other than the two commonly recog- 

 nized, alcohol and carbonic acid; luit it remained for Pasteur to show 

 which were essential, and which were occasional products. In the sries of 

 able papers contributed to the Comptes rendus and to the Anna/es de 

 chimie cl de physique , he proved conclusively that succinic acid and glyc- 

 rine were alwavs found in ferraented solutions of suear, while lactic acid 



o 



and acetic acid, although occasionally prsent, were not alwavs so. Ile also 

 showed that. m addition to thse substances, a part of the sugar was eonver- 

 ted into cellulose and fat. 



The study of the products formed during fermentation opened the way to 

 the second part of the research, \ iz. the cause of fermentation. 



It had been found that certain solutions, when exposed to the air, soon 

 became lull of living organisms : and Pasteur s experiments led him to 

 support the view that thse organisms originated from the prsence of 

 germs Hoatingin the air. Ile found that no living organisms were developed 

 if tare were taken to destroy completely ail those which might be prsent in 

 the solution, and if the solutions were then carefullv sealed up Iree from air. 

 Nor was it necessary to exclude the air, provided that pure air, free from 

 germs, were admitted. By passing the air through red-hot tubes or 

 through gun-cotton before reaching the solutions, he found that the deve- 

 lopinent of organisms, in such boiled solutions, did not take place. An 

 exception to tins was noticed in the case of milk, which required to be heated 

 at a higher temprature than the boiling-point of water at atmospheric 

 pressure. Pasteur showed that this was connected with the alkline reaction, 

 for in ail cases in which the development of life was prevented by heating 

 to the boiling-point of water. the solutions had a faintly acid reaction but 

 that when this was neutralized by carbonate of lime, the solutions then 

 behaved like milk. 



Prof. Pasteur also examined the gun-cotton through which the air lias 



passed ; and he found. among other things, certain cells to which he 

 attributed the power of causing the growth of organisms in solutions. By 

 sowing some of the cells in solutions which previouslv had remained clear, 



1. Proceedings o/ the Royal s,-,ety of London, sance du :;<i novembre 1874, XXIII. 

 L875, p. 68-70 



