6 



THE AMERICAN NATURALIST 



[Vol. LIV 



of human natality, morbidity and mortality, when intel- 

 ligently and broadly studied, can, I am sure, throw a 

 great deal of light on some of the deepest and most sig- 

 nificant problems of general biology. If the facts pre- 

 sented in this paper succeed in some small degree in 

 demonstrating that this opinion is not an entirely idle 

 one, the purpose of this particular piece of work will 

 have been served. 



II 



By an international agreement among statisticians the 

 causes of human mortality are, for statistical purposes, 

 rather rigidly defined and separated into something over 

 180 distinct causes. It should be clearly understood that 

 this convention is distinctly and essentially statistical in 

 its nature. In recording the statistics of death the vital 

 statistician is confronted with the absolute necessity of 

 putting every death record into some category or other in 

 respect of its causation. However complex biologically 

 may have been the train of events leading up to a par- 

 ticular demise, the statistician must record the terminal 

 "cause of death" as some particular thing. The Inter- 

 national Classification of the Causes of Death is a code 

 which is the result of many years' experience and thought. 

 Great as are its defects in certain particulars, it never- 

 theless has certain marked advantages, the most con- 

 spicuous of which is that by its use the vital statistics of 

 different countries are put upon a uniform basis. 



The several separate causes of death are grouped in 

 the International Classification into the following gen- 

 eral classes : 



I. General diseases. 



II. Diseases of the nervous system and of the organs 

 of special sense. 



III. Diseases of the circulatory system. 



IV. Diseases of the respiratory system. 

 V. Diseases of the digestive system. 



VI. Non-venereal diseases of the genito-urinary system 

 and annexa. 



