64 CLOSING OF THE TOES. 



joints has the same effect in the contracting of the 

 muscles which close the toes. This may be seen in 

 those birds which draw up one of their feet, either to 

 w^arm it, or to rest on the other ; for the toes of the 

 foot which is drawn up are always clutched together, 

 and to open them out with the foot in that position 

 requires an effort. It even requires an effort in the 

 bird to keep the toes expanded. When it rests its 

 weight on the feet the weight causes the effort ; but 

 the toes of a dead bird are always partially closed, 

 which shows that a muscular exertion is necessary for 

 keeping them open when that is not effected by the 

 weight. " When the bird is dead, the muscles, which 

 act both ways, are of course equally rigid, and the 

 toes close, to the degree at which the living muscles 

 would balance each other, and the leg be in a state 

 of repose. 



This tendency of the foot to close when the leg is 

 bent is effected in a very simple manner : the ten- 

 dons of the contracting muscles pass over the outsides 

 of the bent joints, and those of the extending ones 

 over the insides ; so that, by the bending, the former 

 are pulled much in the same way as if their muscles 

 were contracted and the latter are slackened in the 

 same way as if their muscles were relaxed. 



All feet which bear on the ground with jointed 

 toes, and partially even those which have hoofs, pos- 

 sess this property, though few of them possess it in 

 the same perfection as the feet of birds. 



And when we consider the difference of habit 

 between clutching, climbing, and perching birds, and 

 quadrupeds which have actions somewhat similar, we 

 can at once see that this property is most necessary 

 in the feet of the birds. Mammalia which clutch 

 prey with their paws have a point of rest for their 



