406 MINOT. (Vou. II. 
ings are small and numerous, constituting the so-called “ Prolif- 
evations-inseln”’:; compare Cut 15. Many of the little thicken- 
ings appear in sections of the villi, Cut 23, a, a, and here and 
there are converted into fibrine, # I have interpreted them 
(Wood's Reference Handbook of the Medical Sciences, V., 695) 
as commencing buds, and consider that in earlier stages they 
grow into branches, but in later stages are in part at least 
arrested in their development. 3°, The proliferation islands are 
converted into canalized fibrine, and at the same time grow and 
fuse, forming larger patches, particularly on the larger stems: in 
this manner are produced the large areas and columns of fibrine 
found in the placenta at four months and after; they have been 
well described by Langhans, and form a striking feature in sec- 
tions of placente. Some of the columns, as stated by Lang- 
hans, stretch along the villi from the chorionic membrane to the 
surface of the serotina as if to act as supports. Ercolani appears, 
if I understand his account, to have seen the fibrine columns, 
without, however, ascertaining either their structure or their 
origin. 4°, Over the tips of the villi, which are bent considera- 
bly where they are imbedded in the decidua serotina, the rela- 
tions are not clear; the epithelium is certainly not present in its 
original form over the imbedded ends of the villi, which are, 
however, surrounded by a hyaline tissue of the character of the 
canalized fibrine, except that the canals are often indistinct or 
even wanting; the hyaline tissue forms an almost continuous 
coat over the decidual surface ; in earlier stages the ectoderm of 
the terminal villi is often considerably expanded. The natural 
interpretation of these facts is that the ectoderm of the villi ex- 
pands over the decidua serotina and degenerates. In this 
manner we account for both the absence of any cellular ecto- 
derm over the ends of the villi and the presence of canalized 
fibrine upon the serotinal surface — but the hypothesis must 
await the final test by observation. 
The ectoderm of the chorion lzve loses by the seventh month 
all traces of the protoplasmic layer, and is without any canalized 
fibrine, except near the placenta; cf zzfra. It is transformed 
into a Zellschicht. In a section of the leve zm sztu at seven 
months, Cut 33, the chorionic ectoderm, c, rests directly upon 
the decidua, which has no epithelium of its own. The ecto- 
dermal cells lie two or three deep; they are described by Kolli- 
