246 REID — ON MORTALITY. 



We must also premise that every individual is at birth endowed 

 with a prospective length of life under favorable conditions, which 

 is measured by the vigor obtained from the parents, modified by a 

 special individuality (for no two members of the same family are 

 alike.) 



This natural life may be prolonged or shortened, owing to the 

 conditions to which it is exposed. One person may naturally die 

 at fifty years, from the wearing out of the mechanisms of life. An- 

 other dying at fifty may have prolonged his term five or more years 

 by extra care and judgment; and others dying at sixty or eighty 

 may have brought on death prematurely, by five, ten, or more 

 years, owing to debilitating influences. 



To take up individual cases as illustration, would far transcend 

 my limited time, and I must deal in generalities. 



Presuming, then, that we have a sufficient knowledge of the 

 most favorable conditions of health, we will compare the present 

 with the past. 



We find by historical evidence that partly owing to increase of 

 numbers, as well as to the fertility of certain districts, population 

 become more dense, and a nomadic merged into a fixed population. 



Deficient drainage and ventilation can scarcely take place when 

 the tent is shifted at frequent intervals ; but it is far different with 

 a stationary house, and the gradual collection of excreta and 

 decomposing material, which, conspiring with war or famine, or 

 both, were sufficient to explain the epidemics which have afflicted 

 humanity from very early dates. 



As wealth increased so did the desire for conveniences and lux- 

 uries, and in time distant countries were laid under tribute to satisfy 

 the demand. This gave rise to the middlemen or merchants that 

 increased in numbers and influence as wealth and ability to pay 

 increased. 



Arising from the same cause, manufactures began to exercise a 

 similar influence, and at the present -these combined have massed 

 very numerous populations about convenient centres or cities, giving 

 conditions the very opposite of what prevailed during the nomadic 

 period. 



