STATISTICS: R. PEARL 
593 
ON THE EMBRYOLOGICAL BASIS OF HUMAN MORTALITY^ 
By Raymond Pearl 
Department of Biometry and Vital Statistics, Johns Hopkins University 
Read before the Academy, November 11, 1919 
I. In order to get a clearer idea of the underlying biological factors 
in human mortality I have rearranged the 'causes of death' listed in the 
International Classification of the Causes of Death, which is the code used 
generally by vital statisticians, into a new classification on a biological 
basis. It is not possible with our present statistical material to make a 
completely and precisely logical classification, but I have endeavored to 
come as close to it as is possible. The underlying idea of this new clas- 
sification is, as the first operation, to group all causes of death under the 
heads of the several organ systems of the body, the functional breakdown 
of which is the immediate or predominant cause of the cessation of life. 
All except a few of the statistically recognized causes of death in the 
International Classification can be assigned places in such a biologically 
grouped list. It has a sound logical foundation in the fact that, biolog- 
ically considered, death results because some organ system, or group 
of organ systems, fails to continue its fimctions. Practically, the plan 
involves the reassignment of all of the several causes of death now 
grouped by vital statisticians under heading *I. General diseases.' It 
also involves the re-distributing of causes of death now listed under 
the puerperal state, malformations, early infancy, and certain of those 
under external causes. 
The headings finally decided upon for the new classification are as 
follows: 
I. Circulatory system, blood, and blood-forming organs 
II. Respiratory system 
III. Primary and secondary sex organs 
IV. Kidneys and related excretory organs 
V. Skeletal and muscular systems 
VI. Alimentary tract and associated organs concerned in metabolism 
VII. Nervous system and sense organs 
VIII. Skin 
IX. Endocrinal system 
X. All other causes of death 
