CRYPTOGAMS 311 
which are the active agents in the making of buttermilk 
and cheese. 
The effects of their rapid multiplication will be better 
appreciated when we consider that bacteria are the smallest 
of known living creatures. If 1000 of the influenza bacilli 
were spread out in a single layer with their sides touching, 
but not overlapping, they would not take up more room 
than one of the periods used in punctuating this book; 
and a coccus concerned in a tubercular disease prevalent 
° (oy @ ear 
> “ve 
2 25 oo 2 = eos Of. 
ds a ee O ogre 
2 6 a C05 Ye A ae 
Qg800 a > O [0% CS ia y! 
Os 9, 0 °o6 1° : ie 
Ores osage ep OL GN B¥ oF 
200 0994 eye oUt 
G02? O CC) vO. 
Ono Ss eo oS Gl Jo Oo =, O 
9 Oo veee ~ 
0° Bso50 SS % 990 fore) Oye! O ie oO 
fer ° Ke) oO = t Oe 
0 PSO 90,28 ‘e) 
445 446 
Fies. 445, 446.— Milk (highly magnified): 445, pure, fresh milk, showing fat 
globules ; 446, milk that has stood for hours in a warm room in a dirty dish, show- 
ing fat globules and many forms of bacteria. 
among cattle in South America has recently been discovered, 
of which double that number could be accommodated in the 
same space. 
352. Distribution of bacteria. — Ordinary air, when free 
from dust, contains, on the average, not more than five 
germs to the liter — equal to about 1 for every 12 cubic 
inches. Pathogenic, or disease-producing, germs seldom 
occur in ordinary fresh air, and even when present are, under 
ordinary circumstances, harmful only to people whose 
bodies, by reason of physical weakness or unhygienic habits, 
offer a congenial soil for their multiplication. Numerous in- 
stances are known in which perfectly healthy persons have 
carried about infectious disease germs in their bodies and 
even transmitted them to others without experiencing 
any inconvenience, or even being aware of their: presence. 
