E 
1876.] Professor Tyndall on Germs. 349 
of Pasteur on the non-continuity of the cause of so-called sponta- 
neous generation, and with other experiments of his own. 
“ On the 9th of November, a second tray, containing one hun- 
dred tubes filled with an infusion of mutton, was exposed to the 
air. On the morning of the 11th, six of the ten nearest the stove 
had given way to putrefaction. Three of the rows 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 contained bac- 
teria, 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 vigor. These differ- 
ences are to be referred to changes in the germinal matter, for 
the same infusion was presented everywhere to the air. Here 
also we have a picture of what occurs during an epidemic, the 
difference in number and energy of the bacterial swarms resem- 
ling the varying intensity of the disease. It becomes obvious 
from these experiments that of two individuals of the same pop- 
ulation, 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. 
“ The author traces still further the parallelism of these actions 
with the progress of infectious disease. The Times of January 
17th contained a remarkable letter on Typhoid Fever, signed 
‘M. D.,’ in which occurs the following remarkable statement : 
‘In one part of it (Edinburgh), congregated together and in- 
habited by the lowest of the population, 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 
ky hospital practice, the opening of a wound during the passage_of a bacterial 
d would have an effect very different from the opening of it in the interspace be- 
u 
% accounted for in this way. Under the heading Nothing new under the Sun, 
essor Huxley has just sent me the following remarkable extract: “ Uebrigens 
kann man sich die in der Atmosphäre schwimmenden Thierchen wie Wolken den- 
ken, mit denen ganz leere Luftmassen, ja ganze Tage völlig reinen Luftverhältnisse 
ae.” (Ehrenberg, Infusions Thierchen, 1838, p. 525.) The coincidence of 
wey 18 surprising, for I knew nothing of Ehrenberg’s conception. My 
Ouds,” however, are but small miniatures of his. 
