INTRODUCTION 213 



INFERIOR EXTREMITY. 



Introduction. Before commencing the dissection the student 

 should be familiar with the bones of the region to be 

 dissected and with the surface markings which indicate the 

 positions of the structures which are to be displayed. He 

 should also possess a general knowledge of the constitution 

 and distribution of a spinal nerve. 



The bones of the inferior extremity are : The os coxce or 

 hip bone ; the femur or thigh bone ; the patella or knee-cap ; 

 the tibia and fibula, which are the bones of the leg ; seven 

 tarsal and five metatarsal bones, which are the bones of the 

 foot ; and fourteen phalanges, which are the bones of the 

 toes, three for each except the great toe, which has only two 

 phalanges (Figs. 101, 102, 103). 



The os coxce. or hip bone lies in the lower part of the trunk. 

 It is jointed posteriorly to the vertebral column, whilst in 

 front it meets its fellow of the opposite side in the median 

 plane, at the symphysis pubis. The upper part of the os coxae 

 is called the ilium. Its highest part forms a curved ridge, 

 the crest of the ilium, which is easily felt at the side of the 

 body and is a little below the level of the elbow when the 

 arm hangs by the side. The posterior end of the crest of the 

 ilium is the posterior superior spine of the ilium. The anterior 

 end of the crest is the anterior superior spine of the ilium. 



The lower and posterior part of the os coxae, upon which 

 the body rests in the sitting posture, is the ischium ; it is a 

 landmark of importance when the posterior part of the 

 inferior extremity is being dissected. 



The lower and front part of the os coxae is the pubis. It 

 meets its fellow of the opposite side, in the median plane, at the 

 symphysis pubis, where it is easily felt. From the upper end 

 of the symphysis pubis a ridge, called the crest of the pubis, 

 runs laterally and terminates in a projection termed the 

 pubic tubercle. 



A faint groove, called the inguinal sulcus, extends from the 

 pubic tubercle to the anterior superior spine of the ilium. It 

 indicates the separation between the lower or inguinal region 

 of the trunk and the upper or subinguinal region of the 

 front of the thigh. If pressure is made along the line of the 

 inguinal sulcus, elastic resistance will be felt; it is due to 



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