304 RESPIRATION AND EXCRETION 



2. Would such congested areas be more likely or less likely 

 to be susceptible to the attacks of bacteria ? 



3. What, then, is the main danger connected with conges- 

 tions ? Note. It is now understood that colds are infections, 

 and that dampness and drafts are but favoring conditions for 

 their development. 



c. A Common Cause (Advanced Work) 



Observation. What are some of the symptoms of com- 

 mon " colds " ? Note. Colds start as active congestions, thus 

 widening the arterioles with a consequent more rapid flow of 

 blood, finally resulting in a more passive state, with white 

 corpuscles thickly adhering to the internal walls of the 

 capillaries. 



Conclusions. 1. How must myriads of clinging white cor- 

 puscles affect the size of the bore of capillary tubes ? 



2. Show how these tubes now become gorged with blood. 



d. Summary of Hygienic Hints 1 



Avoid arterial dilation in inflamed areas : 

 a. In diarrheal conditions by, 



1. Avoiding heavy meals. Why ? What effect on congestion ? 



2. Light diet. Something easily digested and absorbed. 

 6. In colds by, 



1. Avoiding chilling the skin. Why? Note. Heat increases the 



size of the capillaries of the skin, while cold decreases it. 

 What would become of the blood in the capillaries of the skin 

 if it was driven out by sudden cooling ? 



2. Keeping warmly clad. Why ? 



3. Keeping sleeping rooms well ventilated but not too cold. 



4. Discontinuing cold baths temporarily, if such had been the 



habit. Why ? 



5. Avoiding all dampness. Why ? 



6. Keeping the full share of the blood in the skin. What might be 



the effect if even the feet were permitted to become chilled ? 



7. Breathing fresh ar, but not at the expense of chilling the skin. 



1 Adapted from Hough and Sedgewick, The Human Mechanism. 



