36 APPLIED BIOLOGY 



The oviducts are a pair of long, much-coiled, white-colored tubes, 

 lying close to the dorsal wall of the body-cavity and at the sides of 

 the kidneys. Posteriorly they open into the terminal part (cloaca) 

 of the intestine, while anteriorly they have funnel-shaped openings 

 into the body-cavity dorsal to the liver. There is no direct connec- 

 tion between the ovary and the oviduct, but the ova, when ma- 

 ture, fall into the body-cavity, pass through the above-mentioned 

 openings into the oviducts, and then to the exterior through the 

 cloaca. 



The fat-bodies are tufts of bright-yellow masses attached to the 

 dorsal side of the body-cavity behind the liver. The fat is food 

 stored for use in the early spring. Such fat-bodies are found only 

 in frogs and their near relatives, but other animals store fat in 

 various organs. 



Nervous System. (D or L) Remove all the organs which have 

 been studied and cut aw y the floor of the mouth. Notice (I) the 

 skull, which is covered on its ventral surface by the roof of the niouth, 

 and (2) the backbone or vertebral column. The skull contains the 

 brain, and the backbone is a tube which incloses the spinal cord. 

 Looking at the body-cavity side (i.e., ventral), notice the large 

 nerves which extend from the vertebral column to the fore and hind 

 limbs ; also some small nerves extending out to the body-wall 'of 

 the back. Examine brains which have been hardened by chemicals 

 and then removed, and also observe a specimen of a frog dissected 

 from the dorsal side to show brain and spinal cord. 



The bones (skeleton) of the frog may be studied later in compari- 

 son with those of some other backboned animals. The chief bones 

 of the frog can be identified by comparing a skeleton with Fig. 4. 



The muscles of the frog's legs should be examined as to their 

 attachments to the bones. Also, note how shortening of muscles 

 would affect the movements of bones to which they are attached. 

 There are other muscles in the body- wall, and in the walls of stomach, 

 intestine, and blood-tubes. 



37. Organs of Frog. Summarizing, we have found the 

 frog to be made up of parts or organs as follows : - 



Alimentary organs : mouth, mouth-cavity, pharynx, 

 esophagus, stomach, small intestine, large intestine (includ- 

 ing cloaca), liver, and pancreas. 



Breathing organs : nostrils, mouth-cavity, pharynx, 

 trachea, lungs, and skin. 



