ooth, and an external ear is also absent. The remarkable
looseness of the frog's skin is due to great lymph spaces between it
and the body wall.

Section 2. If we now compare the general anatomy of the frog (vide
Sheet 11) with that of the rabbit, we notice that the diaphragm is
absent (Rabbit, Section 4), and the body cavity, or coelom, is, with
the exception of the small bag of the pericardium round the heart, one
continuous space. The forked tongue is attached in front of the lower
jaw, and can be flicked out and back with great rapidity in the capture
of the small insects upon which the frog lives. The posterior nares
open into the front of the mouth-- there is no long nasal chamber, and
no palate, and there is no long trachea between the epiglottis and the
lungs. The oesophagus is less distinct, and passes gradually, so far
as external appearances go, into the bag-like stomach, which is
much less inflated and transverse than that of the rabbit. The
duodenum is not a U-shaped loop, but makes one together with the
stomach; the pancreas lies between it and the stomach, and is more
compact than the rabbit's. There is no separate pancreatic duct, but
the bile duct runs through the pancreas, and receives a series of
ducts from that gland as it does so. The ileum is shorter, there is no
sacculus rotundus, and the large intestine has no caecum, none of
the characteristic sacculations of the rabbit's colon, and does not loop
back to the stomach before the rectum section commences. The
anus opens not upon the exterior, but into a cloacal chamber. The
urinary and genital ducts open separately into this cloaca, and
dorsally and posteriorly to the anus. The so-called urinary bladder is
ventral to the intestine, in a position answering to that of the rabbit,
but it has no connection with the ureters, and it is two-horned.

Section 3. The spleen is a small, round body, not so intimately
bound to the stomach as in the rabbit, but in essentially the same
position.

Section 4. Much that we knew of the physiology of the frog is arrived
at mainly by inferences from our mammalian knowledge. Its histology
is essentially similar. Ciliated epithelium is commoner and occurs
more abundantly than in the rabbit, in the roof of the mouth for
instance, and its red blood corpuscles are much larger, oval, and
nucleated.

Section 5. The lungs of the frog are bag-like; shelves and spongy
partitions project into their cavities, but this