ATMOSPHERE IN RELATION TO PUTREFACTION AND INFECTION. 
67 
The tray of tubes proved so helpful in enabling me to realize mentally the distribution 
of germs in the air, that on the 9th of November I exposed a second tray containing 
one hundred tubes filled with an infusion of mutton. On the morning of the 11th six 
of the ten nearest the stove had given way to putrefaction. Three of the row most 
distant from the stove had yielded, while here and there over the tray particular tubes 
were singled out and smitten by the infection. Of the whole tray of one hundred tubes, 
twenty-seven were either muddy or cloudy on the 11th. Thus, doubtless, in a contagious 
atmosphere, are individuals successively struck down. On the 12th all the tubes had 
given way, but the differences in their contents were extraordinary. All of them con- 
tained Bacteria , some few, others in swarms. In some tubes they were slow and sickly 
in their motions, in some apparently dead, while in others they darted about with 
rampant vigour. These differences are to be referred to differences in the germinal 
matter, for the same infusion was presented everywhere to the air. Here also I imagine 
we have a picture of what occurs during an epidemic, the difference in number and 
energy of the Bacterial swarms resembling the varying intensity of the disease. It 
becomes obvious from these experiments that of two individuals of the same popu- 
lation exposed to a contagious atmosphere, the one may be severely, the other 
lightly attacked, though the two individuals may be as identical as regards susceptibility 
as two samples of one and the same mutton-infusion. What I have already said 
regarding the “ preparedness ” of contagium has its application here. 
The parallelism of these actions with the progress of infectious disease may be traced 
still further. The ‘ Times,’ for example, of January 17 contained a letter on typhoid 
fever, signed “ M.D.,” in which occurs the following remarkable statement : — “ In one 
part of it [Edinburgh], congregated together and inhabited by the lowest of the popu- 
lation, there are, according to the Corporation return for 1874, no less than 14,319 
houses or dwellings — many under one roof, on the ‘ flat ’ system — in which there are 
no house connexions whatever with the street-sewers, and, consequently, no water- 
closets. To this day, therefore, all the excrementitious and other refuse of the inhabi- 
tants is collected in pails or pans, and remains in their midst, generally in a partitioned- 
oflf corner of the living-room, until the next day, when it is taken down to the streets 
and emptied into the Corporation carts. Drunken and vicious though the population 
be, herded together like sheep, and with the filth collected and kept for 24 hours in 
their very midst, it is a remarkable fact that typhoid fever and diphtheria are simply 
unknown in these wretched hovels.” 
The analogy of this result with the behaviour of our infusions is perfect. On the 
30th of November, for example, a quantity of animal refuse, embracing beef, fish, 
rabbit, hare, was placed in two large test-tubes opening into a protecting-chamber con- 
extraet : — ‘ Uebrigens kann man. sich die in der Atmosphare schwimmenden Tbiercben wie Wolken denken, 
mit denen ganz leere Luffcmassen, ja ganze Tage vollig reinen Luftverhaltnisse wechseln.’ (Ehkeebeeg, ‘Infu- 
sionstbierchen,’ 1838, p. 525.) Tbe coincidence of phraseology is surprising, for I knew nothing of Ehbeh- 
beeg’s conception. My ‘ clouds,’ however, are but small miniatures of his. 
MDCCCLXXVI. L 
