POST-MORTEM INTRAUTERINE CHANGES. 293 



translucent, remains unknown to me, but it is not impossible that the reaction of 

 the amniotic fluid is the controlling factor. 



In slightly older specimens the first marked changes in external form resulting 

 from maceration sometimes are seen near the abdominal attachment of the um- 

 bilical cord, as illustrated in No 1523 (fig. 70, plate 5, Chap. IV), an embryo of 

 19 mm. Several blebs are sometimes located on opposite sides of the cord or 

 surround it, as in the case of No. 1475, shown in figure 54 (plate 5, Chap IV). 

 It is interesting that large blebs not infrequently are present in this location, even 

 if the body of the cyema has suffered relatively little change. The size of these 

 blebs, to be sure, may be considerable and, instead of local edema, the entire 

 epidermis may be lifted and the entire cord may be swollen, but such a condition 

 usually arises only later, during longer periods of retention. Sometimes the whole 

 nuchal region is edematous, forming a marked prominence far above that nor- 

 mally present, or is occupied by a single large bleb. For some reason these blebs 

 are common, especially on the head, the dorsum, and on the umbilical cord. 



Sometimes a prominence on the dorsum is due to the swollen, macerated, and 

 completely disintegrated central nervous system, which may form a marked ridge, 

 as illustrated by No. 521/, shown in figure 208, a specimen in which lumbar spina 

 bifida was present. Not infrequently, however, a marked prominence in the 

 upper dorsal region is due to collapse of the brain and drooping of the head, as 

 illustrated in No. 175, a cyema of 13 mm. This collapse of the central nervous 

 system occurs most frequently in the brain of older specimens and is not infre- 

 quently followed by collapse of the calvarium in younger specimens. It may 

 result in marked cutaneous depressions or sulci, as illustrated in No. 1250, a speci- 

 men 13 mm. in length (fig. 209). Rarely, these sulci or ridges may extend entirely 

 down the dorsum of young specimens. 



It is decidedly significant that some intrauterine changes in external form 

 can be simulated by post-mortem extrauterine changes. This is splendidly illus- 

 trated by figures 210 and 211, which are photographs of a fresh and well-preserved 

 and a poorly preserved cat embryo respectively. Similar changes have also been 

 produced experimentally by incubation in sterile solutions, and are further illus- 

 trated by No. 1358/, shown in figures 212 and 213. The former shows the appear- 

 ance of the somewhat macerated specimen before staining and preservation in 

 alcohol, which very materially shrunk the tissues, as shown in the latter. Were 

 the history of this case unknown, one would have been justified in calling it a 

 rather decidedly soft, macerated specimen. Nor do two specimens of identical 

 age, which existed under identical conditions, necessarily present exactly the same 

 appearance. This is well illustrated by Nos. 2258a and 22586, single-ovum twins, 

 shown in figure 214. 



The relatively early loss in detail in the normal relief of the cyema is illus- 

 trated extremely well by No. 2014 (fig. 215), an embryo 17 mm. long. The normal 

 relief of this specimen is replaced by a molding due to maceration. These changes, 

 which are noticeable over the entire body, show particularly in the eyes and ears 

 and in the gaping mouth. The effacement of the normal features in young speci- 



