THE FROG Al 
The paired epicoracoids are two cartilages lying between the 
median ends of the coracoids and precoracoids. 
The sternum proper, consisting of a rod of cartilage ensheathed 
in bone, projecting posteriorly from the epicoracoids, and a some- 
what bilobed plate of cartilage comprising the posterior end of 
the sternum. 
2. The fore-limbs. When the limbs of the frog are extended 
at right angles to the body with the palms of the hands and the 
soles of the feet downward, the anterior sides are called preaxial 
and the posterior sides are called postaxial. (See Bourne, Com- 
parative Anatomy, vol. 1, fig. 5.) The same side is preaxial or 
postaxial whatever the position of the limb. 
With the exception of the small bones of the wrist and ankle, 
all the bones of the limbs are elongated, with enlarged ends capped 
with articular cartilage. The enlarged ends or epiphyses ossify 
independently of the shaft or diaphysis, with which they do not 
unite until late in life. The femur (thigh bone) is a good 
example of a long bone. Examine a dry femur split lengthwise 
and observe that it is hollow. What are the mechanical advan- 
tages of the cylindrical form of the long bones? 
Each anterior limb consists of three parts, upper-arm, fore- 
arm, and hand. The proximal part of the hand is distinguished 
as the wrist. 
The upper-arm or brachium contains a single bone called the 
humerus. This is a good example of along bone. The proximal 
end or head of the humerus rests in the glenoid cavity, forming 
a ball-and-socket joint, and is held in position by muscles and 
ligaments The strong ridge on the preaxial side of the proximal 
portion of the diaphysis is called the deltoid crest or ridge, and 
serves for the attachment of muscles. At the distal end is a 
spheroidal surface for articulation with the bones of the fore- 
arm. Draw a side view of the humerus (X 4). 
The fore-arm contains likewise but a single bone, the radio-ulna. 
This is formed by the fusion of two originally distinct bones 
(compare the human skeleton). The distal half is imperfectly 
divided by a groove into preaxial or radial, and postaxial or ulnar, 
portions. The proximal end is hollowed out to articulate with 
