INTERNAL ORGANS 
87 
of which is attached to the dorsal wall along the line of the 
backbone and the other to the stomach and intestine. A 
small gland (the spleen) is found in this mesentery. The 
spleen has no duct connecting it with any other organ in the 
frog. Blood vessels run through the spleen, which scientists 
believe is important in making new blood corpuscles. 
Lungs. — The lungs are hollow sacs that lie back of the 
stomach, one on each side. In the freshly killed animal, 
these can be filled with air by 
inserting a blow-pipe into the 
windpipe and blowing air into 
them. The empty lungs are 
about as large as the blunt end 
of a lead pencil. 
Kidneys. — The kidneys are 
small red bodies lying close to 
the back. Each one is connected 
with the cloaca by a minute duct 
(ureter or urinogenital duct). 
The urinary bladder is attached 
to the cloaca (Figure 73). 
Reproduction. — The male frog 
has a pair of spermaries (sper'ma- 
riz), one attached to the front 
(anterior) end of each kidney 
(Figure 73). Each spermary (testis) is yellow in color. 
The sperms escape through the kidney. In the female 
frog ovaries, sometimes filled with eggs, are easily seen. A 
long, closely coiled pair of oviducts (o'vi'dukts) opens in 
front near the forward end of the stomach and in the back 
into the cloaca. The eggs break through the wall of the 
ovary and enter the oviducts. As the eggs pass down 
through the oviducts, they are coated with a jelly-like cover¬ 
ing that swells in the water. This jelly covering protects 
the eggs. 
Diagram to show the rela¬ 
tions of the testes to the kidneys 
and the relation of the kidneys 
to the intestine (cloaca). 
