PUTREFACTION AND INFECTION. 121 



hence 30 layers of tubes 6 inches apart might be placed 

 one above the other between the floor and ceiling. 

 This would make 1,296,000 tubes. If only a single 

 germ a day fell into each tube, this would be the number 

 of the germs. If the number deposited were one an 

 hour, we should have thirty millions a day sown in the 

 tubes. Probably the average time necessary for infec- 

 tion is very much less than an hour. At all events, 

 30,000,000 of germs daily would be an exceedingly 

 moderate estimate of the number falling into our thirty 

 layers of tubes. This, moreover, would only be a frac- 

 tion — probably a small fraction^of the germs really 

 present in the air. In his Presidential Address to the 

 British Association at Liverpool, Professor Huxley ven- 

 tured the statement that myriads of germs are floating 

 in our atmosphere. Certain experimenters have rashly 

 ridiculed this statement. In view of the foregoing 

 calculation it, however, expresses the soberest fact. 

 Indeed, taking the word myriad in its literal sense of 

 ten thousand, it would be simple bathos to apply it to 

 the multitudinous germs of our air. 



§ 27. Some Experiments of Pastern* arid. their Rela- 

 tion to Bacterial Clouds. 



Quite recently I had occasion to refresh my memory 

 of Pasteur's paper published in the ' Annales de Chimie ' 

 for 1862. The pleasure I experienced on first reading 

 it was revived by its reperusal. Clearness, strength, and 

 caution, with consummate experimental skill for their 

 minister, were rarely more strikingly displayed than in 

 this imperishable essay. Hence it is that during recent 

 discussions, in which this and other labours of the 

 highest rank met with such scant respect, those in 

 England most competent to judge of the value of scien- 



