VITAL STATISTICS. 699 



which diseases of similar type or character affect the population. It 

 will be sufficient to mention its first great class that of zymotic dis- 

 eases. This term zymotic is derived from a Greek word meaning 

 ferment, and has reference to a change analogous to that of fermenta- 

 tion occurring in the blood by the infinite multiplication of disease- 

 germs. Such affections chiefly comprise fevers par excellence the 

 epidemic, endemic, and contagious or infectious disorders which 

 suddenly attack masses of people, which spring from different sorts 

 of malaria, or from specific communicable poisons ; contaminate the 

 atmosphere and water, and decimate in a brief time civil and military 

 communities. We read in sacred history of whole armies having 

 been suddenly swept away, as that of Sennacherib, which, while be- 

 sieging Jerusalem, lost 185,000 men in a single night under the deadly 

 breath of the destroying angel a beautiful metaphor, probably, for 

 the swift and invisible blow of the pestilence. It has been well re- 

 marked that these diseases distinguish one country from another, one 

 year from another. They have formed epochs in chronology, and, as 

 Niebuhr has shown, " have influenced not only the fall of cities, such 

 as Athens and Florence, but of empires." 



This great class of maladies is the index of salubrity ; it is this 

 class which varies to the greatest extent in different climates and 

 seasons, which modifies the fatality of other kinds of disease, and 

 which constitutes the principal difference between the health of differ- 

 ent peoples and periods. 



A general and uniform system of death-registration among nations 

 renders easy what would otherwise be impracticable, viz., constant 

 international exchanges and comparisons, not simply confined to in- 

 dividual affections, but applicable as well to immense groups of cog- 

 nate diseases. In this manner statistics of mortality assume vast im- 

 portance, and present for our consideration manifold questions of a 

 physical, social, and political character. They determine the laws 

 which regulate the duration of life ; they indicate in what manner 

 those laws have been or are being infringed, and afford bases for cal- 

 culations materially affecting the interests of mankind. Statistics are 

 far from being the barren array of figures ingeniously and laboriously 

 combined into columns and tables, which some persons are apt to 

 consider them. They constitute rather the ledger of the people, in 

 which, as the merchant in his books, the citizen can read at once all 

 the results of a week, a month, a year, or series of years, and can de- 

 duce the profit or the loss which has accrued to the account of vitality, 

 morals, education, wealth, power. And it has been well said that 

 " science has nothing to offer more inviting in speculation than the 

 laws of vitality, the variations of those laws in the two sexes at dif- 

 ferent ages, and the influence of civilization, occupation, locality, sea- 

 sons, and other physical agencies, either in generating diseases or in 

 improving the public health." 



