322 THe MICROSCOPE. 
Convenient culture tubes, and very cheap ones, are tall hom- 
eopathic vials, which are to be stopped with cotton batting. No 
sterilizing is necessary, nor the precautions needed for pure 
culture experiments. For the purpose these would be a hind- 
rance. The only apparatus needed is one or more balances and 
a few graduated flasks for making the solution, and the reagents 
for making Pasteur’s fluid. 
In preparing the liquids for the flasks, the process was con- 
stantly the same, viz: 
Pasteur’s With Sugar.......ccceoncoscscesedasesovecvonascesssoyaenssn 8 parts. 
Waid yeast. ............s-ccesecoccssccccedectvcscssodcdasartcssevusesns 1 part. 
Se edog ies od wissieensteaeuu tated Vesta ch a dhoa's sa teas ouske Lomee tees 1 ae 
Fluid yeast was made by mixing evenly one-half gramme of 
compressed yeast with 100 c. c. of distilled water. * stands for 
any reagent the effect of which is to be tried. In the first three 
classes of experiments it was water, and in the fourth it was 
various matters to be described later. I shall now proceed to 
describe briefly the actual experiments. 
First serres.—In this series four experiments were made, viz: 
1. Yeast, 1; distilled water, 9. 
2. Yeast, 1; 10 per cent. solution cane sugar, 9. 
3, Yeast, 1 ;. Pasteur’s solution without sugar, 9. 
4. Yeast, 1; water, 1; Pasteur’s fluid with sugar, 8. 
These being the customary and well known experiments I 
will not delay to remark on the results.* 
SEconpD sERIES.—This consisted of three experiments to test 
the effect of heat and cold on yeast. Three tubes were prepared, 
one being set aside as a standard, while a second was set out of 
the window over night, and the third was boiled gently for five 
minutes. The third and first were at once brought together, and 
on the following day the second was added. The second had 
been frozen for twenty-four hours, the thermometer having been 
below zero F. all the time, and in the night at—10° F. These 
were allowed a week} in which to grow, and on examination one 
and two were found to be equally vigorous, while three had not 
grown any. The naked eye convinced one of the trait which 
the microscope confirmed, for tubes one and two were turbid 
*One student, who was in advance of the others, made a series of trials to show the 
adyantage of the presence of a minute trace in Pasteur’s fiuid of potassium nitrate, 
calcium sulphate, etc., but no positive results were reached in the time at her disposal. 
t This was the date necessitated by the students’ college time-schedule, In some of 
the experiments an examination after forty-eight hours would haye been desirable. 
