A HUMAN EMBRYO (MATEER) OF THE PRESOMITE PERIOD, 



BY GEORGE L. STREETER. 



INTRODUCTION. 



In the literature there may be found descriptions of 16 very young and appar- 

 ently normal human ova, containing embryos in which the somites have not yet 

 made their appearance. These specimens are all accompanied by authentic clini- 

 cal data. There are, in addition, 4 presomite specimens which are probably normal, 

 but in which clinical data are missing. When one arranges all of these specimens 

 in their apparent order of development they will be found to fall into three clearly 

 defined groups: First, those in which the primitive groove has not yet appeared; 

 second, those in which there is a primitive groove but no neurenteric canal; and 

 third, those in which the neurenteric canal and medullary groove can be definitely 

 recognized. It has been my privilege to examine a well-preserved, normal speci- 

 men which would belong to the second of these groups, and in this paper I wish to 

 present a survey of its main morphological features. The specimen has been 

 temporarily deposited in the Carnegie collection for the purpose of this study, and 

 has been listed in the catalogue as embryo No. 1399; it will be referred to, however, 

 as the Mateer embryo, in recognition of the owner, who, appreciating the embryo- 

 logical importance of the specimen, brought it to our attention. 



HISTORY OF SPECIMEN. 



The ovum was obtained by Dr. Horace N. Mateer, of Wooster, Ohio, from a 

 fibroid uterus which had been removed by Dr. H. J. Stoll, of Wooster, 11 days after 

 the woman had missed her menstrual period. The patient, a white American, aged 

 39 years, had been married 17 years. This was her fourth pregnancy, and there 

 had been no abortions or evidence of venereal disease. She is of a prolific family, 

 the mother having had 17 children, and a sister 10 children. The following men- 

 strual history of the case was obtained at the time of operation : 



Sept. 10, menstruation began. 



Sept. 12, menstruation ended. 



Sept. 19, coitus. 



Sept. 27, coitus. 



Oct. 8, menstruation expected but failed to appear. 



Oct. 19, hysterectomy. 



It may be added that the patient had been informed by Dr. Stoll of the pres- 

 ence of the fibroid condition and warned that in case she became pregnant it 

 would be necessary to remove the uterus. It is therefore probable that she made 

 careful note of such matters and that the above clinical data may be relied upon. 



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