1 26 Physiology. 



liness, plenty of direct sunshine, care in diet, and the keep- 

 ing of the body in good tone, reduce the chances of 

 "taking" contagious diseases. An open-air life, abundant 

 nutritious food, and freedom from anxiety are probably the 

 best cures for the first stages of consumption. 



Destruction of Germs by Colorless Corpuscles. The 



colorless blood corpuscles may take these germs of disease 

 into their substance, and destroy or change them so that 

 the disease is warded off. In other words, they may be 

 compared to a cat that catches and eats the mice which 

 invade a house. 



Germs killed by Plasma. Sometimes the blood con- 

 tains a substance that kills or prevents the action of dis- 

 ease germs. Such a substance is called anti-toxin, which 

 means a counteracting poison. But the blood of most 

 persons does not naturally contain anti-toxin, and so, if the 

 disease germs gain entrance, the disease follows. 



Vaccination. Vaccination is the introduction of an anti- 

 toxin. That it is a " poison against poison" is shown in the 

 fact that one is likely to feel some bad effects after vaccina- 

 tion. If the anti-toxin is successfully introduced into the 

 blood, the person is usually safe from the disease. A per- 

 son seldom has the smallpox more than once. This is 

 because when he has the disease the germs in their growth 

 produce an anti-toxin, which remains in the blood, and 

 keeps these germs from growing in that blood again. The 

 material used in vaccination is called vaccine lymph, and is 

 obtained from cows, in whose lymph it is produced. 

 Physicians now vaccinate or inoculate against a number 

 of diseases by introducing the proper anti-toxin. 



Danger of getting Germs into Wounds. There is danger 

 of introducing germs of disease in so simple an act as pick- 



