DEPARTMENT OF EMBRYOLOGY. 109 



Among the abortions during the first month only one-fifth of the 

 specimens contain normal embryos; from those in the second month 

 over one-half, and in the third and fourth months eight-ninths of the 

 embrj^os are normal. Beyond this the table is of little value for statis- 

 tical purposes, as a very large number of normal foetuses obtained by 

 physicians are not sent to us. A study of the membranes shows that 

 many of those encircling embryos, although normal on first appearance, 

 are diseased, thus accounting for the abortion. The cause of this 

 diseased condition is undoubtedly a previous venereal infection or in 

 some cases perhaps a puerperal infection associated with a former 

 childbirth. (See Mall, Journal of Morphology, vol. 19, 1908.) 



The study of pathological embryos has been continued and all that 

 bear catalogue numbers from 400 to 500 have been prepared for micro- 

 scopic examination. This work will have to be continued slowly for 

 a number of years before a final comprehensive report can be made. 

 Meanwhile the results obtained from an examination of 117 specimens 

 of tubal pregnancy should be published during the coming winter. 



The statistical study of the normal form has been undertaken by 

 Franklin P. Mall and by Michael Reicher. The latter has completed 

 about 12,000 anthropological measurements on 385 specimens as a 

 basis of an exact study of the growth of the body and its proportions; 

 the data concern chiefly the foetuses from the beginning of the ninth 

 week until birth. In each instance 23 standard anthropological meas- 

 urements of the head and 20 of the body were taken. About one-third 

 of the material for his study was placed at Dr. Reicher's disposal by 

 the Anatomical Departments of the University of Minnesota, the 

 University of Chicago, and the University of Michigan. For this 

 kindly cooperation we are indebted to Professors C. M. Jackson, R. R. 

 Bensley, G. W. Bartelmez, and G. C. Huber. 



A preliminary report on the study of the form, classification, and 

 age of embryos less than 25 millimeters long has been made by Franklin 

 P. Mall. It is quite apparent why it is difficult to determine in a 

 satisfactory way the age of human embryos; the time of fertilization 

 is practically impossible to ascertain, as we do not know with certainty 

 when ovulation takes place, and even if this were known it would still 

 remain to be determined how soon after ovulation the sperm-cell enters 

 the egg. Of course, we know in a general way that conception probably 

 begins near a menstrual period, but here again there is a difference of 

 opinion of nearly a month, as it is uncertain whether we should count 

 from the last period or from the first lapsed period. 



The evidence which bears upon this subject has been brought 

 together in Chapter VIII of the Manual of Human Embryology, edited 

 by Keibel and Mall. In order to compare the obtainable data, it was 

 necessary to consider anew the question of measuring human embryos. 



