248 STUDIES ON PATHOLOGIC OVA. 



the villi belonging to the respective vesicles at a point where they come in closest 

 contact. An examination of this area shows that the ovum giving rise to the smaller 

 conceptus was embedded independently, although undoubtedly also contempo- 

 raneously with the larger. Hence this specimen can not be rightly regarded as 

 one of superfetation. 



The next specimens of twin pregnancy which might be regarded as a case of 

 superfetation are Nos. 788 a and b, donated to the Carnegie Collection by Dr. 

 Anfin Egdahl. These twin chorionic vesicles, which were almost of the same 

 size, measured 60 by 45 by 40 and 60 by 55 by 40 mm., respectively. Although 

 of approximately the same size, the former contained a stunted embryo 17 mm. 

 long, the latter a nodular one only 3 mm. long. The differences in size and in 

 the character of the two embryos are so marked that they prompted Mall to 

 make special inquiry of the donor as to whether these chorionic vesicles were 

 really obtained from the same patient, as reported. This inquiry Dr. Egdahl 

 was able to answer promptly and positively in the affirmative. Here we are again 

 dealing with a case of twin pregnancy, in spite of the fact that the size of the em- 

 bryos might seem to indicate that we really have a case of superfetation under 

 consideration. But that the case is not such is shown also by the fact that the 

 chorionic vesicles practically are of the same size. The smaller abortus with a 

 partially inverted chorionic vesicle containing the better preserved of the twins is 

 shown in figure 21 (plate 3, Chap. IV). Figure 19 (plate 2, Chap. IV) shows the 

 appearance of the larger abortus, which contained the smaller nodular embryo 

 only 3 mm. long. The latter is seen at a midpoint near the upper third of the 

 illustration. Both illustrations are practically of natural size. The larger fetus, 

 the external form of which was fairly preserved, had an approximate age of about 

 48 days, as estimated by the Streeter (1921) curve. Mall noted that the organs 

 could all be outlined, but that they were dissociated, and that the mandibular 

 region had fused with the skin of the thorax. The small nodule, which represents 

 the only remnant of the embryo belonging to the larger chorionic vesicle, contains 

 a large cavity, with thick, fibrous walls, but nothing save epidermis and a remnant 

 of the nervous system could be recognized. 



A far more convincing instance of apparent superfetation was found in a 

 specimen of twins donated by Dr. Jane Ross of Binghamton, New York. The 

 fetuses, Nos. 1840 a and b, contained in this abortus are shown in figures 151 

 and 152. The larger measured 31 mm., but the smaller only 15 mm., indicating 

 respective ages of 63 and 45 days. The chorionic vesicles belonging to these twins, 

 which formed a single mass, are shown in figures 153 and 154. The incised vesicle 

 containing the smaller fetus is shown in figure 154, and the larger vesicle, which 

 is somewhat inverted, in figure 153. Since the latter had been opened and the 

 larger fetus exposed, I at first overlooked the smaller fetus and found it only at a 

 subsequent examination made for the purpose of determining the cause for the 

 peculiar consistency and appearance of this portion of the abortus. The condition 

 of the smaller fetus, which is well revealed in figure 152 under a magnification of 



