No. 3. ] UTERUS AND EMBRYO. 413 
“The capillaries of the villi are remarkable for their large 
size, and on this account have been described as arteries or 
veins by E. H. Weber, Goodsir, and other writers. Their calibre 
is often sufficient for from four to six blood-disks abreast. They 
are very variable in diameter, and also peculiar in exhibiting 
sudden restrictions and dilatations, Cut 
27, In the short bud-like branches 
there is often only a single capillary 
loop, but as the branch becomes larger, 
the number of loops increases, and 
they form anastomoses. In branches 
large enough to serve as a stem, some 
one or two of the vessels may be en- 
larged, as may be seen in Cut 27; in 
the branches large enough to admit of 
it, there are two (or sometimes only 
one) longitudinal central vessels, an ar- 
tery and vein, and a superficial network 
of capillaries, Cut 27@. Goodsir and 
other early writers laid great stress on 
the formation of the capillary loops, but 
this feature is a common one in the de- 
velopment of the foetal vascular system, 
as is also the width of the capillaries. 
In my opinion these peculiarities are 
characteristic rather of the foetus than 
: Cut 27a. Placenta of about 
specifically of the placenta. In some of gy months; ay cone? Seal 
the older writers (Goodsir, Farre, e¢ a/.) villus, to show the central ves- 
it is asserted that the true capillary sys- sels and superficial capillaries. 
tem disappears toward the end of ges- * 105 diams. 
tation. I am unable to confirm this, but find instead that in 
the slender terminal villi of the placenta at term there is often 
only a single, sometimes long, capillary loop; the capillary is 
very wide, and its width is probably the reason of its having 
been held formerly to be a vein or an artery.” 
§ 16. Uterus during menstruation. — I have little to add to 
the descriptions of previous authors, particularly those of 
Leopold, 36, and Kolliker.t It is, however, worth while to pre- 
sent the accompanying illustration, Cut 28, since there is a lack 
1 K6lliker’s Handbuch der Gewebelehre, 5te Aufl., p. 563. 
