STRUCTURE OF THE HUMAN BODY SKELETON. 9 



and the shoulder-blade behind. The clavicle can be felt under the 

 skin above the chest on each side, and can be seen very well 

 outlined in thin persons. The shoulder-blade is a flat triangular 

 bone, surrounded by the flesh of the back, find it can also be 

 seen very well in very thin people. It is not fixed, and follows 

 the motions of raising and lowering the arms. The upper arm 

 and thigh have only one bone ; that of the thigh is called the 

 femur. The fore- arm and leg hav.e two bones placed alongside 

 of one another ; the hand and foot have a great number. The 

 fingers and toes are divided into three parts called phalanges ; the 

 thumb and great toe have only two phalanges. 



The bones of the limbs, for facility of movement, rotate on 

 their extremities by means of a kind of joints called articulations. 

 The shoulder, the elbow, the hip, and the knee, are the principal 

 articulations ; the phalanges are also all articulated together. 

 The surfaces of the bone which thus slide one upon another are 

 perfectly smooth, and in addition are always kept moistened by 

 a sticky and oily liquid, which prevents their being rubbed 

 together too roughly. 



In order to complete our study of the skeleton, we ought to 

 speak of organs which are not so hard as the bones, and 

 which also serve for a solid framework for the flesh ; we mean 

 the cartilages. The solid and elastic portions of the ear, and the 

 sides and end of the nose are formed of cartilages. They are 

 also formed at the extremity of all the ribs, which are osseous 

 behind, and always cartilaginous in front. 



MUSCLES. The Muscles form the principal part of what is 

 called flesh ; they are red in man as well as in the ox 

 and horse, but are much paler in the sheep, the calf, and 

 especially in the fowl. The muscles consist of fleshy masses, 

 generally long, and continued at both ends by what are called 

 tendons. The largest and best known in the body is that which 

 ascends from the heel to the calf of the leg, and is called the 

 tendon of Achilles. The calf is formed by a muscle attached above 

 to the thigh, and which is continued below by the tendon of 



