Human Physiology. 



animals. Shut up a plant in darkness, and see what comes of 

 it. Only the fungi can so flourish. In partial darkness there 

 may be a pale weak growth, but no flowers or fruit. Shut up 

 the strongest man in a dark dungeon, and he becomes pale 

 like a corpse, his blood loses its vitality, and he is liable to 

 scrofulous diseases. He loses the power of resisting diseasing 

 influences. The cholera finds its greatest proportion of victims 

 in the narrowest and darkest lanes and courts. There are great 

 differences in its mortality between the sunny and shady sides 

 of the same streets. Sunshine strengthens all, and is a power- 

 ful medicine for many diseases. A sunny exposure, plenty of 

 large windows, and no blinds or curtains, are important con- 

 ditions of health. Early rising is healthful, chiefly because by 

 that means we live more in the light. Night is the time for 

 rest and sleep, because we can then best spare the invigorating 

 influences of the day. The fashion that turns night into day, 

 diminishes health and shortens life. 



Air is the first condition of independent life. There is no 

 life without air. During gestation, the mother breathes for her 

 child ; her lungs receive the oxygen that reddens its blood ; but 

 from birth to death we breathe every moment, and our health 

 depends very largely upon the quantity of the air we breathe, 

 and upon its purity. When the air is impure we breathe less. 

 In the foetid air of crowded assemblies, in unventilated churches, 

 theatres, or school-rooms, we instinctively limit our breathing 

 to the least quantity that will keep us alive. We take in poison 

 with every breath, and yet we must breathe. When we come 

 out, what expansion of the lungs, what draughts of pure fresh 

 air! The result of our bad-air poisoning may be a cold, or 

 diminished health for days. What we need for health is a full 

 and constant supply of pure air at all times sleeping and 

 waking by night and by day. Night is the time to sleep ; and 

 in sleep we do not need the stimulus of light but we need 

 pure air as much as by day. The blood demands its oxygen 



