WEIGHT, SITTING HEIGHT, HEAD SIZE, FOOT LENGTH, AND 

 MENSTRUAL AGE OF THE HUMAN EMBRYO. 



By George L. Streeter. 



Before any satisfactory growth curve for the human embryo can be constructed 

 or the normal range of its variations in the different stages of development can be 

 determined, more abundant and better data are necessary, as has long been apparent 

 to those concerned with this problem. As a means towards this end, all of the em- 

 bryological material received at this laboratory during the past five years has been 

 systematically weighed and measured and, in order that the individual records 

 may be comparable, the methods and conditions have been maintained as nearly 

 uniform as possible; in fact, the determinations were made for the most part by 

 the same person. The data thus derived from 704 selected specimens have been 

 tabulated and plotted in the form of fields and graphs and are now presented in 

 the hope that, in addition to their value in the study of normal growth, they may 

 be of aid in the recognition of such abnormal and pathological processes as are fre- 

 quently met with in specimens from abortions. Furthermore, since much of the 

 material was accompanied by clinical records of the menstrual age, it has been 

 possible to construct an age scale which can be read for weight and size simultane- 

 ously. The consideration of both of these factors will make it possible to estimate 

 more accurately than heretofore the age of embryological specimens, it having been 

 necessary in the past to base the estimation either on size or on weight alone. Fur- 

 ther than the making of a few selected measurements which can be easily carried 

 out in any laboratory, no attempt is made in this paper to enter into a more detailed 

 anthropological consideration of fetal growth. That important field is at present 

 being studied by Dr. A. H. Schultz, who has made comprehensive observations upon 

 these and additional specimens. 



The ideal material for determining the curves of fetal length, weight, and age 

 would be living specimens (examined in the fresh state) which had been removed 

 by operation at chosen intervals in cases where there was a recorded single coition 

 immediately following menstruation. With abundant material of this character 

 from normal individuals of the same age, stature, race, and living conditions, 

 each of whom had previously borne the same number of children, we might well 

 expect perfect results. However, these requirements, although they can be 

 met in all other mammals, can not be met in man. In the latter, therefore, we 

 must be content with conditions that are as nearly constant as possible for the bulk 

 of the material obtainable. The observations reported in the literature can not 

 be assembled satisfactorily because of lack of uniformity in the technique adopted 

 by the various observers in making measurements and in the method of preserving 

 the material. The data on age are usually scant and the criteria as to whether or not 

 the specimens are normal are frequently unreliable. The best available data are 



