« ib =

During the process of nourishing themselves, micro-organisms injure
ian. The manner in which this is brought about is:

(a) By production of soluble toxins or poisons (diphtheria).
(b) By production of insoluble toxins due to splitting up of proteins

of body.

(c}) By mechanical action.

Infections may be: (2) Local-—boils; (») Gceneral--typhoid fever,

Infections may spread by (a) etnies Co) blood stream, (c) lymph

strean.

References: Storey--Defensive Hysiene, Book II, Chapters 17 and Lee

Rice, T. Be—Conguest of Disease, Chapter 2.
Bossard——Problems of Social Well-Being, Chapters 8, 9, 15.
Chapin, C. Ve—-Sources and Modes of Infection, Chapters 4-8,
Dekrui Microbe Hunters.
Radot--Life of Pesteur,.

dhe a

DISCUSSION QUESTIONS:

 

1.

Re

Se

4.

Be ee cab

Which one of the groups of exciting causes of ill health do you
consider most important today?

Is there any change going on at the present time in the relative
importance of these groups? What? Why?

What would happen if we destroyed all of the bacteria?

How do bacteriologists proceed when they wish to decide whether a
disease is canmunicable or not?

In what way are disease producing bacteria most frequently spread
from one person to enother?

What information is it necessary to have about a given bacteria in
order to provide defensive measures against it?

What conditions determine whether an individual who takes patho-
genic organisms into his »ody will become ill?

Compare the process of fermentation with microbic disease?

low do bacteria harm the human body?

 

Certain persons who are exposed to communicable diseases do not
come dom with them; other persons recover from them. This raises two
cuestions which are of great practical importance to every individual-—
resistance ard immunity.