COPULATORY ORGANS OF THE AMNIOTA. 
1.5 
vessels. No branches are sent to the cloaca, the arms, or to the copulatory organ. 
This break between an essentially vasomotor and an ordinary visceral supply taking 
place between a and ft coincides fairly well with the end of the rectum and the 
beginning of the interior cloacal chamber s. urodseum. 
Microscopic examination of osmic preparations of the various nerves mentioned 
above showed the following':— 
Nerves supplying the M. caudi-ischiadicus.—The ordinary somatic structure. 
Nerves of stem ft, supplying the rectal wall.—Consisting of two portions, one non- 
medullated, the other with, fine medullated fibres. 
Nerves to the penis.—Many non-medullated (“ sympathetic ” vaso-motor), and 
many fine medullated (visceral) fibres ; the whole nerve agreeing exactly with a 
typical N. erigens in structure. 
A piece of nerve of the lateral sympathetic chain between y and S agrees much with 
the rectal branches from ft ; it is a visceral nerve with small medullated fibres, and a 
large amount of non-medullated fibres. 
In the Lizards the anal and sexual muscles are likewise supplied by postsacral 
nerves, which chiefly belong—like in the Crocodiles—to stem a in Monitor, Cnemido- 
jphorus, Hatteria; or to sterns a+ 8 in Cyelodus, Platydactylus, Lacerta viridis, 
Ojphryoessa, Poly ohms ; or to stems a-\-ft in Cho/m/de on. 
The cloacal region in Emys is supplied chiefly by the 22nd-f- 23rd-f- 24th nerves, i.e., 
y+S + e, the penis by the 24th and 25th = e-f~ Q. The same formula applies to 
Testudo groBca. AH. these cloacal and copulatory nerve-branches run between the 
cloacal lateral walls and the M. lumbo-caudalis and M. pubi-caudalis, branching off 
from the whole spinal nerve-stems near the middle line. 
III. The Modifications of the Cloaca. 
The internal or cephalic end of the cloaca of the Crocodilia is marked by a very 
prominent ring-wall (fig. 23, re), which is produced by the concentration of the circular 
muscular fibres. Somewhat half-way between the cephalic end and the anal opening 
is another fold (fig. 22, F), chiefly formed by the submucosa of the cloacal walls, most 
prominent on the dorsal side. These two semi-lunar folds are frequently so high and 
well developed that their opposite lips touch each other. They divide the whole 
cloaca into two chambers. The anterior, inner or cephalic, one has the same coatings 
as the rectum, but its inner walls are smooth and different in structure from the 
rectum. Into the dorso-lateral sides the ureters open separately, just above a promi¬ 
nent papilla. This chamber is either empty, or filled with the clear, almost colourless 
urine, which can distend this “urinary chamber” into an oval shape of very large 
size. It never contains faeces, which only pass through it. Such a chamber is 
peculiar to the Crocodilia. At the first glance we should compare it either to the 
chamber UD, or, because of its shape and partial function, to the chamber CD of 
