
"EXPERIMENTS WITH SALINE SOLUTIONS 243 
solutions similar, except that they contained a 
drop or two less of the dilute phosphoric acid, or 
what comes to much the same thing, a little more 
of the alkaline sodium silicate. The boiled acid 
solution will be productive, while the boiled slightly 
alkaline fluid is much more likely to be barren—again 
contradicting the data of Pasteur, founded on his 
more limited experience with this class of experi- 
ments. When I began in 1906 to repeat such experi- 
ments I did not at first attach sufficient importance 
to this point, and the result was that a considerable 
number of the tubes in which the fluids were slightly 
alkaline yielded negative results. 
This point is, indeed, so important that great care 
is necessary in preparing the solutions. The ordin- 
ary sodium silicate solution is so tenacious that Mr 
Martindale! has mixed the quantity sent to me with 
equal parts of distilled water. This at first forms 
a very opalescent fluid, but in the course of 
an hour or less the solution becomes a clear, watery- 
looking liquid. In the preparation of the experi- 
mental fluids, the same dropper has been used for 
the silicate of soda solution and for the other two 
fluid chemicals employed (namely, the dilute phos- 
phoric acid or the liquor ferri pernitratis), when one 
or other of these has been required ; though it has 
been cleaned with distilled water each time before 
being used for a different fluid. With the dropper 
employed, ten drops of water exactly equalled ten 
minims as measured ; and the same was found to be 
1 Of 10 New Cavendish, W., from whom my chemicals and dis- 
tilled water for these experiments have always been obtained. 
