170 On the Relations between Mind and Muscle. 



lost centre, our admiration must rise still higher. But although the process 

 of equilibration is essentially instinctive or involuntary, it may be much 

 assisted by voluntary exertions and practice. No instinctive feeling or 

 motion could keep a person balanced on a tight rope, on the first occasion 

 of trying that position. The constant use of this feeling in some of our 

 ordinary movements is very striking. Let us take that of walking, for 

 instance, and endeavour to analyse it. The very first action is a shift- 

 ing of the centre of gravity, which would otherwise be lost in the subse- 

 quent movements. To prevent such an occurrence, the weight of the head 

 and trunk is thrown upon one inferior extremity, instead of being shared 

 between the two. After this has been accomplished, the other leg is bent, 

 raised, projected, and replaced on the ground : when replaced it is in a 

 state of extension. The next movement is to throw the centre of gravity 

 into a perpendicular between the legs, by rotating the posterior leg on the 

 foot, and bending the anterior knee. The weight is then shifted to the 

 anterior limb, by raising the heel of the hinder foot, (which acts as a lever 

 of the second order) the leg being kept in a state of extension by the same 

 action, so as to form a sort of inflexible rod for pushing the pelvis forwards. 

 Lastly, the hinder leg is bent, raised, and brought up to the other. This 

 is the analysis of a single step, the constituent movements of which require 

 comparatively little nicety of equilibration ; but in walking, the weight of 

 the body is not only transferred from one limb to the other without any 

 intermediate rest, but while poised on the one, suffers a motion of rota- 

 tion on the head of the thigh bone, of much greater extent than in the 

 former instance, because the hinder limb is not replaced upon the ground 

 when it has come into a line with the other, but is kept suspended and 

 projected. During the latter process, the weight of the limb and the action 

 of the muscles which throw the body forward, tend to disturb the equilibri- 

 um ; the weight tending to one side and the propulsive force to the other. 

 The walk of aged and feeble persons consists of a succession of steps, 

 because in these movements there is less muscular power required, both in 

 balancing the body and in projecting the limbs. A person who either from 

 weakness or from intoxication does not enjoy a full command of his mus- 

 cles, or in other words, whose muscles do not act in harmony with the 

 feelings peculiar to equilibrium, has a rolling gait, occasioned by one leg 

 passing in front of the other. This action results from a want of the 

 natural adjustment between the propulsion, the rotation, and the tranfer- 

 ence of the weight. 



Giddiness is the loss of the feeling of support ; but what is the cause of 

 the natural feeling of support, or equilibrium ? On first putting this ques- 

 tion, it might seem to be answered by saying, that the feeling in question 

 is only that of pressure in a particular part of the body. The whole weight 

 of the system resting on so small a surface as the sole of the foot, must 

 occasion considerable pressure ; and although we have ordinarily no con- 



