OF STANDING AND WALKING. 453 



sumed, the contractile power of muscles may be restored by furnishing 

 them, through a suitable arrangement, arterial blood; for this fact we 

 are indebted to Dr. Brown- Sequard, his experiments having been made 

 both upon man and animals. The arterial blood employed assumed, 

 during its passage through the limb which was the subject of the trial, 

 the venous character, and issued of a dark color. This restoration of 

 contractility was by no means imperfect or transient ; in one instance it 

 continued for two hours. 



By means of tendon the muscles are attached to the skeleton, which 

 constitutes the solid framework of the system. Operating Connection of 

 thus through the skeleton, the muscles are enabled to keep muscle for lo- 

 the entire body in the erect or standing position, and also to 

 give it locomotion. The conditions of standing and locomotion have been 

 well studied by the brothers Weber, the following being a brief synopsis 

 of their statements. 



In man, the power of standing implies the conservation of the line of 

 direction of the whole body within the narrow basis covered by 



mi i i i Of standing. 



the feet and between them. The head is balanced on the at- 

 las so nearly under its centre of gravity that no ligamentum nuchse is 

 required, as in the case of other animals, to prevent it from falling for- 

 ward. Nevertheless, a forward motion can be executed, amounting to 

 about 75 degrees from the perpendicular, and a lateral motion right and 

 left of from 45 to 50 degrees. In standing, the weight of the entire body 

 is transmitted perpendicularly to the feet. These rest on the heel and 

 the. fore ends of the metatarsal bones, especially of the great and little 

 toes, and on the points of the toes. The general centre of gravity of the 

 entire body is a little above the transverse axis connecting the heads 

 of the thigh bones, and for equilibrium to be maintained, a perpendicular 

 line drawn from this centre must always fall within the basis inclosed by 

 the contour of the feet. 



Even in the most perfect condition of rest that we can assume while 

 maintaining the standing position, a great many separate muscular acts 

 are necessarily required. Apart from those little voluntary changes 

 which are incessantly occurring, the rhythmic action of the muscles in- 

 volved in respiration, especially those of the abdominal walls, is perpet- 

 ually changing the position of the centre of gravity, and therefore those 

 muscles which are employed in keeping the spine erect are obliged to 

 assume an antagonizing rhythmic action. This is at once the reason of 

 the fatigue we experience in long standing, and of the difficulty which 

 infants encounter in their, attempts to maintain the erect position. 



In walking, the legs act like a pair of pendulums. The head of the 

 thigh bone, which is their centre of motion, is held in its sock- 

 et, not by muscular exertion, nor by its ligamentous arrange- 



