n one side of this latter, cut across in front of where
the vein dips down to liver, and peel the body wall away from it. The
xiphisternum will probably be cut in this operation. In early spring the
females are greatly distended with ova, and the greater portion of the
ovary may, with advantage, be removed. The oviduct is dead white
then, and larger and much more in evidence than the (pinkish)
intestine even. Turn over the viscera, and compare with Sheet 11;
one lung is often found greatly inflated, and then projects back into
the body cavity; the stomach is, in some cases, pushed forward and
hidden behind the shoulder girdle. Observe the allantoic bladder, the
spleen, gall bladder, portal vein, and pancreas. By squeezing the gall
bladder gently, the bile duct will be injected with bile, and will be
apparent if the stomach is turned over. The oesophagus, just in front
of the stomach, should be cut through, and the rectum, and the
mesentery and alimentary canal supported by it, removed. This will
expose the urogenital organs. (Vide Figures given.) These vary
greatly, especially in the females, at different seasons. The condition
figured would be seen in late autumn, or winter. In spring females are
often found copulating with males, and then the ovary itself is
inconspicuous, while the lower part of the oviduct is enormously
distended with ova, so as to be mistaken sometimes for the ovary
by those who fail to note that the ova are enclosed by a thin
semi-transparent skin (wall of oviduct). The vena cava inferior is
seen between the kidneys and the renal portal vein beside the ureter.
Cutting through the mesentery supporting the kidney laterally, the
dorsal aorta is exposed, and on either side of it the sympathetic chain
and rami communicantes, often tinged with black pigment.
This black pigment is a frequent but variable feature of the frog's
anatomy, and usually dapples or blackens the testes, and also
sometimes darkens the otherwise pale pink arteries. Behind the
kidneys the sciatic plexus also becomes visible. Careful drawings
should be made. Cut off the head of the frog, shave off top of brain
case, and put the head in strong spirit.

Second Dissection.-- A fresh frog is required. Pin out under water as
before, and open up body cavity. Now carefully remove the muscle
from the ventral portion of the shoulder girdle, to expose the clavicles
and coracoids. Cut away xiphisternum, and then cut through clavicles
and corac