The Frog 77 



The pelvic, ( ) or hip girdle, (Fig. 22) supports 



the hind limbs, and consists of two sets of three parts each, the ischium 

 ( ), ilium ( ), and the pubis 



( ), the latter being cartilaginous, strongly united. 



The edge of the hip girdle is called the crest. The meeting of the two 

 pubic bones forms a symphysis ( ). The anterior 



end of each bone is attached to one of the transverse processes of the 

 arched vertebra. The little cup-shaped opening, where the three bones 

 just mentioned meet, is called the acetabulum ( ). 



It is in this concavity that the head of the femur ( ), 



the long bone in the thigh, lies. 



The hind limb consists of a thigh ( ) with the 



femur as its solitary bone. The leg proper, running from knee to ankle, 

 is made up of the tibia ( ) and fibula ( ) 



fused together, called the tibio-fibula, or leg bone. 



Note the ridges on these long bones for the attachment of muscles. 



There are four tarsal bones ( ), the astragalus 



( ), the calcaneum ( ), and two 



smaller ones. 



The foot has five complete digits as well as an extra or super- 

 numerary toe. Each digit has one proximal metatarsal bone, while 

 beyond these there are a variable number of phalanges. The hallux 

 ( ), corresponding to the great toe of man, is the 



smallest of the series. It has one metatarsal and two phalanges. On 

 the inner side of the hallux is the calcar ( ), an extra 



toe. It may have one or two joints and a short metatarsal. 



THE MUSCULAR SYSTEM 



All movements in the body are produced through the contraction 

 of some one or more muscles. The muscles in turn are innervated 

 ( ) by one or more nerves. The muscle is usually 



attached by one or both ends to a bone, so that a good leverage is 

 obtained. In some cases the attachment is direct. In others the muscle 

 is attached by means of a tendon. A tendon is a band of tough, some- 

 what inelastic, connective tissue which is in reality the continuation of 

 the muscle fascia after the muscle itself ends. 



Contraction may be brought about by many causes, such as heat, 

 pressure, electrical, or chemical stimuli ( ). 



There are three distinct types of muscles (Fig. 23) ; each type has 

 a more or less individual, cellular arrangement. These three types are 

 known as heart muscle, voluntary or striated muscle, and involuntary 

 or nonstriated muscle. 



Striated muscle can be moved when the individual possessing it so 

 desires. Such are the muscles of the arm and hand. Examples of non- 

 striated muscle may be found in the blood vessels, where the desire of 

 the individual has little or nothing to do with the contraction and 



