SP ONTANEO US-GENERATION CONTR VERS Y. 45 5 



sufficed to cause all the floating matter to be deposited on the sides 

 and bottom, where it was retained by a coating of glycerine, with 

 which the interior surface of the case had been purposely varnished. 

 The test-tubes were then filled through the pipette, boiled for five 

 minutes in a bath of brine or oil, and abandoned to the action of the 

 moteless air." 



In this way the air in its normal condition was freely supplied to 

 the infusions, but of mechanically suspended matter it could be de- 

 monstrated that there was none. And it was proved, with a clearness 

 that admits of no quibble, that infusions of every kind, animal or vege- 

 table, were absolutely free from putrefactive organisms. " In no sin- 

 gle instance. . . . did the air which had been proved moteless by the 

 searching beam show itself to possess the least power of producing 

 bacterial life or the associated phenomena of putrefaction." But por- 

 tions of the same infusions exposed to the common air of the Royal 

 Institution Laboratory at a continuous temperature of from 60 to 70 

 Fahr., fell invariably into putrefaction ; and when the tubes contain- 

 ing them amounted to six hundred in number not one of them escaped 

 infection they were all " infallibly smitten." Here is irresistible 

 evidence that there is a direct relation between a mote-laden atmos- 

 phere and bacterial development. The whole series of Dr. Tyndall's 

 exquisite experiments is simply an irrefragable affirmation of this 

 truth. The presence of the physically demonstrated motes is as essen- 

 tial to the production, in a sterilized infusion, of septic organisms, as 

 light is to actinic action. They cannot be made to appear without the 

 precursive motes ; they cannot be prevented from appearing if the 

 motes be there. That these are the germs of bacteria by themselves, 

 or associated with minute specks of matter, approximates to certainty 

 in the proportion of hundreds of millions to one. 



A beautiful illustration of the minuteness and multitude of the 

 particles is given. Let clean gum-mastic be dissolved in alcohol, and 

 drop it into water ; the mastic is precipitated and milkiness is pro- 

 duced. Gradually dilute the alcoholic solution, and a point is reached 

 where the milkiness disappears, and by reflected light the liquid is of 

 a bright cerulean hue. " It is in point of fact the color of the sky, and 

 is due to a similar cause namely, the scattering of light by particles 

 small in comparison to the size of the waves of light." 



Examine this liquid with the highest microscopical power, and it 

 appears as optically clear as distilled water. The mastic-particles are 

 almost infinite in number, and must crowd the entire field of the mi- 

 croscope ; but they are as absolutely ultra-microscopic as though 

 they had no existence. I have tested this with an exquisite -$ of 

 Powell and Lealand's, employed with a new and delicate mode of 

 illumination for high powers, 1 and worked up to 15,000 diameters; 

 but not the ghostliest semblance of such particles was seen. But at 



1 Vide Monthly Microscopical Journal, April, 1876. 



