1007.] on Nerve as a Master of Muscle. 617 



Similarly with the toxin of " lock-jaw." The muscles which close the 

 jaws are much more powerful than those which open them. In the 

 norma] act of opening the mouth the relatively feeble opening muscles 

 contract, and the powerful closing muscles are simultaneously relaxed 

 by reflex inhibition. But in an animal or man poisoned with this 

 toxin the normal inhibition of the closing muscles is changed to the 

 €xactly opposite process of excitation so that their contraction results. 

 Against the power of these strong closing muscles the contraction 

 of" the weak opening muscles can effect little. Each time therefore 

 that the sufferer tries to open his jaws to take food or speak, he 

 clenches his jaws instead of opening them— experiencing a torture 

 which, although unaccompanied by physical pain, is inexpressibly 

 distressing. And the disorder leads to death from inanition. 



But to return to the reflex lifting of the leg, whence we set out. 

 It was mentioned that in this reflex the hmb was not merely lifted, 

 but was slightly rotated inwards at the hip, and that the thigh was 

 slightly abducted, that is to say, drawn sideways, separating it more 

 from the fellow-limb of i,he opposite. These accessory movements 

 have a significance coinciding with much other evidence into which 

 we have not time to enter now. They, together with other evidence, 

 show that this lifting of the leg, so easily produced reflexly, is nothing 

 more nor less than the first movement of the taking of a step. In 

 fact, in our rough and imperfect analysis of this little movement, we 

 have been examining part of the great and extraordinarily complex 

 and perfect act which is called walking— or more technically, so as to 

 include the cognate acts of trotting and running— locomotion. And 

 a little reflection will suffice to assure you that included in the action 

 of locomotion is also that of standing. We are apt to forget that the 

 muscles have a static as well as a kinetic action — that they are 

 the instruments of maintaining position, as well as of the execution 

 of movements. Directly we begin to analyse locomotion we see that 

 its basis, as it were, is the position of standing, upon which move- 

 ments of stepping are, as it were, grafted. Xot much is known as 

 yet of how animals and ourselves stand, walk, and run. In these 

 acts, probably, every skeletal muscle in the whole body is concerned. 

 Rheumatism can make us aware of that. A little receptor organ in 

 the ear is a great factor in the whole matter. But of this we may be 

 sure, that foremost in its factors are reflex actions of the limbs. 

 Great economic questions are involved in this unravelling of the act 

 of locomotion — all beasts of draught and burden are chiefly useful to 

 us because they can stand, and walk, and run. We can only employ 

 their powers to full advantage and with due regard to them as they 

 unfold these powers when we shall have learnt something of the way 

 in which these movements are conducted and performed. 



The crude and imperfect analysis which I have attempted to out- 

 line concerned but one jjhase of the step of a single limb. In the 

 complete act the other limbs will at the same time be executing other 



