Human Physiology. 



crowded and filthy quarters. For one rich man who dies of 

 cholera, there are a hundred of the poor simply because the 

 rich can command the conditions of health, and have, there- 

 fore, the power to resist diseasing influences. Impure air, 

 whether that of close, unventilated rooms, or of close and 

 crowded districts, or that loaded with noxious effluvia, is not 

 only a predisposing cause of zymotic diseases, such as measles, 

 scarlet-fever, diptheria, small-pox, typhus and typhoid fevers, 

 but a direct cause of a great many local diseases, especially 

 those of the lungs, and those depending directly upon the con- 

 dition of the blood, for blood-poisoning comes chiefly from the 

 atmosphere; and the accumulation of matter of disease in the 

 system is caused by the lack of vital force, which prevents the 

 removal by excretion of waste and noxious matter. 



As food, suitable in quality and sufficient but not in excess 

 in quantity, is a condition of health, it follows of necessity that 

 bad food, insufficient food, or too much food must be a cause 

 of disease. No plant, and no animal consequently no man 

 can maintain perfect health without a perfect nutrition. Man 

 can live on a wider range of food than most animals ; but as 

 some kinds of food are better adapted to him than others, are 

 therefore more natural for him, there must be some diet most 

 natural and best adapted to the human constitution ; and every 

 variation from that, in quality or quantity, must be a cause of 

 imperfect health, which is disease. Man has great power ot 

 adaptation. The Esquimaux live on blubber, and some Euro- 

 peans feed on the almost equally greasy and less pure flesh of 

 the fattened swine. Blubber or bacon ? The blubber must be 

 the least harmful. All animals living in unnatural conditions 

 are liable to disease. Pigs, penned in sties, become scrofulous 

 (scrofa, a sow) ; the livers and lungs of fattened hogs and cattle 

 are often filled with tubercles, and their flesh may give tubercu- 

 lous disease to those who eat it ; the hog is also specially liable 

 to one form of tape-worm, as the sheep is to another, and the 



