214 
HAROLD’S DISCUSSIONS. 
milking, in the utensils used. Heat is a great de¬ 
stroyer of germs. If milk is heated to 158° all bac¬ 
teria in it are killed, but the spores require boiling 
for a minute or two ; otherwise they have the power 
to produce new germs. 
This much has here been given on the subject 
of milk because of its importance to health. Conn’s 
Story of Germ Life (D. Ap^^leton and Company) con¬ 
tains an interesting account of the uses and evils of 
bacteria. 
MINUTE ANIMAL LIFE. 
Starting with the yeast, I have given you a glimpse 
of the innumerable plants whose forms are revealed 
only by the compound microscope. Yeast is the most 
common of these, and its action is easily observed. 
How we shall see what animal life the microscope re¬ 
veals. 
Let us dip a glass of water out of a stagnant pool. 
Possibly we have caught up a water-beetle or two, or 
a few wormlike creatures. These are all the life that 
is visible. 
We will take the drop of water and put it on a 
glass slide. It seems to be quite clear and free from 
life; but what wonders the microscope brings into 
view! There are little swimmers moving quickly 
about in the drop. 
A little jellylike speck attracts our attention. In 
appearance it does not differ from a bit of the white 
of an egg. But watch it, and you will find that it 
moves. It stretches out fingerlike points, and the 
