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Vou. IX. TRENTON, N. J.. NOVEMBER, 1889. No. 11. 
EXPERIMENTS IN YEAST: THE PHYSIOLOGY OF NU- 
TRITION. 
HENRY LESLIE OSBORN. PH. D., 
PROFESSOR OF BIOLOGY IN HAMLINE: UNIVERSITY. 
HE following experiments with yeast are described for a two- 
fold purpose: both to record the results of a series of ob- 
servations made by the students in a junior Biology class, and 
to show a convenient method which teachers may employ to 
introduce students to direct biological experimentation. The 
method here indicated can be applied extensively and will yield 
interesting and valuable results. 
Four classes of experiments were performed, and although 
time did not permit the very exhaustive pursuit of any of the 
lines of research entered upon, yet each was pursued far enough 
to yield definite and positive results. The general method used 
was to cultivate yeast in Pasteur’s fluid for one week, to make a 
drawing of a field of the microscope when the yeast was first 
sown, and compare this with the yeast of a week’s growth; 
the degree of complexity of the colonies, their number, and 
the look of the individual yeasts, were all taken ag criteria by 
which to decide on the favorability of the conditions furnished, : 
If necessary to develop differences in the action of the two eon- 
ditions the cultures were kept for several weeks. 
