320 STUDIES ON PATHOLOGIC OVA. 



many ectodermic nodules or proliferating islands. In a conceptus measuring 26.5 

 by 22.0 by 14.5 mm., she found the villi 3 or 4 mm. long, with branches and 

 trunks so oblique that they were almost parallel to the chorionic surface. Accord- 

 ing to her, the villi converge towards the poles of the chorionic vesicle, as stated by 

 Eternod, but possess so variable a form that it is difficult to describe them, the 

 caliber changing from thick to thin, from wide to narrow, from cylindrical to folded 

 so quickly that a single branch sometimes possesses all these characteristics. She 

 found anastomoses fairly numerous, but free villi ending in epithelial prolongations 

 were rare. Most of the anastomoses seen resulted from ectodermic fusion, but 

 villi separated by some distance and united by true villous bridges containing 

 mesoderm were also seen. According to Lazitch, dichotomy occurred in 65 to 

 70 per cent of the villi, trichotomy in 20 to 25 per cent, and a more complex form 

 in 10 per cent. The branching usually was at an acute angle, but branches which 

 diverged 180 also were found. Since buds were present on the chorionic mem- 

 brane, Lazitch concluded that a moderate amount of interpolation of new villi 

 among the old undoubtedly occurs. 



Johnson (1917) found the villi on a chorionic vesicle, containing an embryo 

 with 24 somites, variable in size and 1.1 to 1.3 mm. long in the region of the chorion 

 frondosum. Johnson stated that the villi were usually smaller at the bases, and 

 that smaller villi, although few in number, were found among the larger. 



Ingalls (1918) also found the villi on a chorionic vesicle 9.1 by 8.2 by 6 mm. 

 to vary greatly in size and shape, but stated that the chorionic vesicle seemed to 

 be covered by them over all of its surface. This finding of Ingalls seems to be in 

 accord with observations upon the best-preserved and youngest specimens in the 

 Carnegie Collection. Small chorionic vesicles, with one or two opposite bare areas, 

 and others with sparsely set villi, are not rare, but at present we possess no evidence 

 establishing the strictly normal nature of these specimens. Among these speci- 

 mens is the vesicle represented in figure 7 (plate 1, Chap. IV). Isolated and 

 sectioned villi from this specimen show the presence of but slight branching and 

 rather cylindrical villi. The absence of some of the villi in this specimen is due 

 to the mechanical means used in the removal of the blood-clot before the specimen 

 was received. 



A vesicle which, though macerated, deviates only very slightly from the nor- 

 mal, is No. 1878, the exterior of which is represented in figure 232 (plate 19, Chap- 

 ter XIII), and the portion bearing the embryo in figure 233. As seen in the 

 latter figure, these young villi look unusually matted and bulbous, though it 

 must be remembered that young villi necessarily are united and covered by 

 trophoblast in which they are implanted. Some isolated specimens of these 

 villi are represented in figure 242, and what especially strikes one's attention is the 

 presence of an exceedingly fine basal portion in the villus to the left. Although 

 the caliber of normal young villi varies considerably, I do not believe that such 

 forms as this can be regarded as strictly normal, and this belief is confirmed by an 

 examination of sections of the villi, shown in figures 243 and 244. It is possible 

 that maceration alone is responsible for some deviation from the normal form of 



