218 STANDING. 



for the erect position, and that its weight falls within the 

 base of support, the feet, and therefore if formed of a 

 single piece like a marble statue, would stand without the 

 need of other assistance. But it is to be recollected 

 that the body is composed of various pieces, connected 

 together by joints that are easily bent by the superincum- 

 bent weight, and that consequently this tendency must be 

 counteracted by suitable provisions. These provisions 

 are found in the action of the muscles. 



Emily. How is this the muscles bend the joints, 

 and therefore the more strongly they act, the more diffi- 

 cult will it be for the body to keep erect. 



Dr. B. There are muscles, not only to bend the 

 joints, but others whose office it is to bring the limbs 

 back again to their unbent position. The former are 

 ca\\ed flexors, the latter extensors. Generally, the body 

 when left without support of any kind, has a tendency to 

 fall forward, and if we examine the connexions of some 

 of its parts, we shall immediately see the cause. 



Emily. I recollect you mentioned that the head 

 slightly preponderated forward, and this I suppose, as- 

 sists in the general preponderance of the whole body in 

 that direction. 



Dr. B. In standing therefore, the muscles on the 

 back part of the neck are strongly exerted to maintain 

 the head erect. The weight of the organs in the chest 

 and abdomen, has a tendency to carry it forward, which 

 is counteracted by the long and powerful muscles on the 

 back. The whole weight of the trunk is now transmit- 

 ted to the hip-joint which would be inevitably bent were 

 it not prevented by muscular action ; thence it is trans- 

 mitted to the knee joint and finally to the ancle joint, both 

 which are kept from bending by the same means. So 

 that in standing there is a constant and wearisome exer- 

 tion of the muscles to prevent the parts from bending on 

 each other, and preserve the general equilibrium of the 

 body. 



Emily. I might have known better, if I had but re- 



