116 A HUMAN EMBRYO BEFORE THE APPEARANCE OF THE MYOTOMES. 



One carries away from the perusal of the literature bearing on the age of young 

 ova the relations between ovulation, menstruation, fertilization, implantation, 

 etc. the impression that the actual age of a normal embryo has a value, for pur- 

 poses of classification at least, more apparent than real if not in large measure 

 fictitious, and the more so because this assigned age can be only a more or less defen- 

 sible approximation. Complicating the more general factors touched upon above 

 are the individual variations and peculiarities, pathological states it may be of the 

 maternal organism if not. also of the future ovum, temporary bodily or seasonal 

 conditions and the like, not to mention possible paternal influences, a variety of 

 factors which it is difficult or impossible to evaluate, and we are imperceptibly 

 carried into problems of fecundity, absolute and relative sterility, and other clinical, 

 racial, and sociological questions. In the end one can appreciate the perplexity of 

 Hyrtl when he wrote long ago in his characteristic vein: "So weit ware nun Alles 

 recht. Nur begreifft man dabei nicht, warum die Frauen nicht fortwahrend 

 schwanger sind, und aus dem Schwangersein ihr Lebelang nicht herauskommen." 



The entire specimen was stained in bulk with hematoxylin, and after sectioning 

 at 10 microns was counterstained with eosin-safranin. The plane of section, 

 which it was supposed would be transverse to the embryo, the interior of the vesicle 

 having been examined somewhat before embedding, came out quite obliquely, as 

 can be seen in the various text-figures. While the staining reactions are not 

 always what could be desired, still there is no doubt that the essential features have 

 been preserved. Occasional mitoses are in evidence, as will be noted later. 



I. THE CHORIONIC VESICLE, GROSS. 



The following account is taken from our notes made soon after receiving the 

 specimen. The intact vesicle (plate 1, figs. 1 and 2) is quite regularly formed and 

 distinctly flattened; the surface showing the circular area of free villi is slightly more 

 convex than the opposite. The form tends to be roughly quadrangular with the 

 corners rounded off. To the touch the vesicle feels quite firm and resistant. Meas- 

 ured under a magnification of 5 diameters, the ovum shows the following dimensions : 

 length 9.1 mm., breadth 8.2 mm., thickness 6 to 6.5 mm. The internal measure- 

 ments are from 1 to 1.5 mm. less. 



One surface of the ovum presents a large, sharply defined area of free chorion 

 and its villi, situated at one end and extending about to the middle. These villi 

 vary greatly in size and shape. They may assume the form of long, slender proc- 

 esses or of thick, broad, irregular masses, often in clumps together and leaving a few 

 small areas free. There are a few straw-colored areas as from blood-stains. The 

 remainder of this surface of the ovum is smooth and varies in color from a straw 

 through a red (fresh meat) to almost a purple. 



The opposite side of the ovum is much smoother, covered partly by a much 

 thinner layer of maternal tissue through which project more or less freely the villi 

 of the chorion. These villi appear to be rather more pointed and slender than those 

 previously noted, resembling papillae filiformes. There seems to be no part of the 

 sac which does not possess villi. 



