BALANCE WHEN ASLEEP. 429 



proper membranes and sheaths, lie the muscles of 

 the fowl's leg. These are variously arranged so as to 

 move the limb in the actions of walking, scraping, 

 &c. But one of these, a thin muscle, sends its 

 tendon downwards in such a manner over first the 

 knee joint, and next the projection of the heel, 

 that, when the weight of the body bends the leg 

 downwards, this tendon is immediately put on the 

 stretch, and so draws the toes firmly together, by 

 this means not only enabling the bird to preserve 

 an exceedingly firm hold of its perch, but also 

 doing so without the least fatigue to the muscles 

 of the limb. It is wonderful to think how even 

 with this beautiful and simple contrivance the 

 balance of the bird is preserved when it is fast 

 asleep ! The balance of our own bodies, although 

 we have two excellently formed feet for standing, 

 is nevertheless only sustained by a continual 

 succession of involuntary muscular actions. When 

 we think we are standing firmly without any 

 muscular effort, we are in fact all the time balancing 

 ourselves in a very wonderful and singular manner. 

 This is the cause why when persons are suddenly 

 taken with some fatal internal seizure, though 

 standing perfectly still, they immediately fall to 



