REPORT OF THE DEPARTMENT OF EMBRYOLOGY.^ 



Geouge L. Strketer, Director. 



During the past year a study of the correlation between weight and 

 measurements for the human fetus at the different stages of its develop- 

 ment has been brought to a conclusion. The ideal material for a study 

 of the growth of the embryo and for the determination of the correla- 

 tion of length, weight, and age would be normal living specimens, re- 

 moved by operation at chosen intervals following a single recorded 

 coition, in cases where there is an accurate menstrual history. Further- 

 more, the specimens should have come from individuals of the same 

 age, race, and stature, whose living conditions were identical, and who 

 had previously had a like number of children. Although these formid- 

 able requirements can be fulfilled in other mammals, they can never, 

 of course, be completely met in man. In the latter, therefore, we must 

 be content with conditions that can be kept as nearly constant as possi- 

 ble for the bulk of the available material, and for results we must rely 

 upon mean curves taken from a large number of specimens, rather than 

 on observations upon individual ones. 



This laboratory is fortunate in being the recipient of continuous ac- 

 cessions of human embryos in all stages of development, thus making 

 it possible to inaugurate a plan of systematic examination whereby the 

 factors of fixation and the technique of weighing and measuring may be 

 kept uniform. During the past five years, by working with these im- 

 proved methods, we have accumulated data sufficient for the construc- 

 tion of new and more adequate curves of fetal growth and for the deter- 

 mining of the normal ranges of variation at different periods of de- 

 velopment. Of all embryological material examined, 704 specimens 

 were selected as normal and sufficiently well preserved for accurate 

 measurements. The results derived from these have been plotted and 

 published in the form of tables, fields, and graphs. In addition to 

 their importance in the study of normal growth, these data promise to 

 prove of value in the recognition of the abnormal and pathological 

 processes that are frequently met with in aborted specimens. More- 

 over, since most of the selected cases were accompanied by clinical 

 records of the menstrual age, it has been possible to construct a much 

 more accurate age scale than has heretofore been available. 



I will not describe here the particular technique employed in weigh- 

 ing and measuring the specimens, a full account of which is contained 

 in the completed paper. Mention may be made, however, of two im- 

 provements in the methods of measurement which have been devised 

 in this laboratory during the course of these investigations. 



'^ Address, Carnegie Laboratory of Embryologj', Johns Hopkins Medical School, Baltimore, 

 Maryland. 



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