+1876.) 
Professor Tyndall on Germs. 351 
development in an infusion, infected by either a speck of liquid 
containing bacteria or a drop of water, is extraordinary. On 
January 4th a thread of glass almost as fine as a hair was 
dipped into a cloudy turnip infusion, and the tip only of the 
glass fibre was introduced into a large test-tube containing an in- 
fusion of red mullet. Twelve hours subsequently, the perfectly 
pellucid liquid was cloudy throughout. A second test-tube con- 
taining the same infusion was infected with a single drop of the 
distilled water furnished by Messrs. Hopkin and Williams; 
twelve hours also sufficed to cloud the infusion thus treated. 
Precisely the same experiments were made with herring, with 
the same result. At this season of the year, several days’ expos- 
ure to the air are needed to produce so great an effect. On De- 
cember 31st a strong turnip-infusion was prepared by digesting 
thin slices in distilled water at a temperature of 120° Fahr. The 
infusion was divided between four large test-tubes, in one of 
which it was left unboiled, in another boiled for five minutes, in 
the two remaining ones boiled and, after cooling, infected with 
one drop of beef-infusion containing bacteria. In twenty-four 
hours the unboiled tube and the two infected ones were cloudy, 
the unboiled tube being the most turbid of the three. The infu- 
sion here was peculiarly limpid after digestion ; for turnip it was 
quite exceptional, and no amount of searching with the micro- 
“cope could reveal in it at first the trace of a living bacterium ; 
still germs were there which, suitably nourished, passed in a 
single day into bacterial swarms without number. Five days 
have not sufficed to produce an effect approximately equal to 
this in the boiled tube, which was uninfected, but exposed to the 
common laboratory air. 
“ There cannot, moreover, be a doubt that the germs in the air 
differ widely among themselves as regards preparedness for de- 
velopment. Some are fresh, others old; some are dry, others 
moist, Infected by such germs, the same infusion would require 
different lengths of time to develop bacterial life. This remark 
applies to and explains the different degrees of rapidity with 
which epidemic disease acts upon different people. In somé, the 
hatching period, if it may be called such, is long, in some short, 
the differences depending upon the different degrees of prepared- 
ness of the contagium.” 
