YORKSHIRE VETERINARY MEDICAL SOCIETY. 7? 
putrefaction and producing living germs of animal or vegetable 
origin is contained in the atmosphere, although it is invisible and 
indistinguishable; and he shows further that if this ordinary air be 
passed over the flame of a spirit-lamp, the floating matter is no 
longer apparent; having been burnt up in the flame, it is no longer 
capable of developing animal life ; it is therefore organic matter 
which is destroyed. The same disappearance of particles followed the 
slow passage of air through a red-hot platinum tube. These organic 
dust-particles would appear to be the rafts which support the 
contagium of an epizootic or enzootic disease, and thus it is floated by 
currents of air; for we find that a heated body which merely 
increases the temperature of the air, but does not consume it, 
expands ; becoming specifically lighter, it ascends , but the organic 
dust-particles or germs are left behind, below. It is thus clearly 
shown that the life-giving germs, poison, or whatever it may be 
occupies the lowest stratum of the air. This is of the utmost 
importance for veterinary surgeons to know ; it is nothing less than 
a practical means sketched out to us by which we may in future 
destroy both these adventitious matters and the contagium. I do 
not presume to say that an atmosphere entirely freed of this 
organic and inorganic matter would necessarily be more wholesome 
to be constantly inhaled by our domestic animals. It would seem 
that Professor Tyndal is of opinion that it would be beneficial, from 
the fact of his recommending cotton respirators, in order to free the 
air as we breathe it of all these impurities. I believe that there is 
not a place in which the atmosphere is wholly free from them, 
therefore it may be said to be its normal condition. But this is an 
ascertained fact, that whenever these spores or germs, or miasmatic 
veins, exceed a certain proportion in the air, it is abnormal, and in 
the same ratio is disease more or less prevalent and fatal. 
Professor Tyndal has further proved the above facts by an 
ingenious experiment, viz. if you allow a strong ray of light to 
pass through a small hole into a dark chamber containing ordinary 
air, it is quite visible all the way across the chamber ; this is owing 
to the refrangibility of the air containing solid organic particles or 
vibration of atoms, which become luminous as the ray strikes them ; 
but if the air in this chamber is rendered perfectly pure by the 
mechanical removal of these solid particles and germs, the ray of 
light will be utterly invisible. This experiment shows that pure 
air is invisible by its own intense transparency. This is a proved 
and an acknowledged fact; it is a confirmation of the opinion 
formed by all scientific men, viz. that if man could be transported 
into that intense blue boundless space beyond the photosphere of 
this earth’s atmosphere, where all is eternal breathless silence, he 
would find himself surrounded by absolute and impenetrable dark¬ 
ness. There being no atmosphere, no constituents of an atmo¬ 
sphere—nothing, in fact, for a ray of light to act upon, the rays 
would pass through that vast region utterly invisible. 
I have already shown you that I believe each of the forms of 
influenza are dependent upon causes differing somewhat in their 
