208 
HAROLD’S DISCUSSIONS. 
Fig. 100. — Ba¬ 
cillus which 
makes milk 
sour. 
see, she made it in the same waj and kept it under 
the same conditions as she had at other times when it 
was good. She says she can not account for it. The 
scientist, however, has discovered that the conditions 
were not exactly identical; he has found other organ¬ 
isms besides yeast in the sponge. At times these are 
more numerous than at others, and 
then they produce evil effects. 
The vintner sometimes finds his 
wine turning acid or bitter, becoming 
ropy, or acquiring a moldy taste. The 
same is true of beer. Investigations 
have proved that these undesirable 
effects, and others as well, are due to 
the presence of plant organisms very 
similar to the yeast germs. Other kinds are found 
in milk, and turn it sour ; others cause meat to decay ; 
still others produce sores where the skin is broken or 
cut, etc. 
The air is full of these minute organisms; the 
water is alive with them, and the soil contains them 
in abundance to the depth of four feet. They far 
outnumber the plants to be seen with the eye. 
Many of them are so small that twenty-five hun¬ 
dred can be placed side by side in the space of one 
inch. Since they are so tiny, it is no easy task to 
study their structure, and their species can not well 
be determined. They may be grouped into three 
classes by their general shape. Under the magnifier 
a large class of them resemble lead-pencils, some cut 
square at the ends, others sharpened or rounded. 
