470 ZOOLOGY. 
into the cloaca. In the salamanders the end of the oviduct 
serves asauterus. There are also fat-bodies (Fig. 433) at- 
tached to the anterior end of the reproductive glands of the 
toads and frogs, the use of which is unknown. For a gene- 
ral idea of the structure of Amphibians the student should 
dissect a frog or toad in connection with the following de- 
scription and accompanying illustration (Fig. 483), prepared 
by Dr. C. 8. Minot.* 
The frog is one of the types of Vertebrates most valuable 
to the student, being readily obtained and easily dissected. ' 
The accompanying figure represents the anatomy of the 
spotted or leopard frog, Rana halecina, male. 
The skin is smooth, having neither scales, feathers, nor 
hairs, and contains numerous microscopic glands, of which 
there are said to be two kinds—one having an acid, the other 
an alkaline secretion (L. Hermann). It is pigmented on 
the dorsal surface, but whitish underneath. The head is 
broad, triangular, with two large nasal openings in front, 
large and prominent eyes, two tympanic membranes formed 
by a part of the integument stretched across a hard ring, 
and an enormous mouth. The neck is short and not con- 
stricted, The body tapers slightly posteriorly, and has the 
opening of the cloaca upon the posterior end of its back. 
Hach limb consists of the three divisions: in the front leg, 
brachium, antebrachium, and manus with four digits, of 
which the fourth is very much thickened in the male; the 
sexes may be distinguished by this mark. In the hind leg 
the three divisions are the femur, crus, and pes, with five 
Jong digits, between which the membranous web is stretched. 
If the web is examined in a living frog with a microscope, 
the circulation of the blood in the capillaries can be studied. 
The current of corpuscles and plasma is constant, and in a 
given vessel passes only in one direction ; by following the 
stream backwards and forwards it will be found to issue 
from larger vessels, the arteries, and to enter into other and 
different vessels, the veins. The pigment corpuscles can 
also be seen in the web ; they are branching bodies, capable 
of drawing in or expanding their processes, and they can be 
made to contract by an electrical shock from an induction 
apparatus. 
* Also see Ecker’s Anatomy of the Frog; and the manuals of Mivart 
and of Murshall; also Huxley and Martin’s Biology. 
