x. FLITTERMICE. 141 



toes of the feet, and like them bears a sharp curved claw 

 by which on occasion the creature can suspend itself, and 

 which comes into use when it is shuffling along the 

 ground. 



There is a curious inverted position of the hind-limb, 

 observable when the bat is thus shuffling along, which I 

 will very briefly describe and then have done with these 

 (I hope not wearisome) structural details. Unlike the 

 monkey and the vast majority of the mammalian class in 

 which the knee is directed forwards, the bat has its leg 

 screwed round in such a way that the bend of the knee is 

 in just the opposite direction. Our little flittermouse has 

 its thigh so twisted upwards and backwards as to bring the 

 hind-limb into the position exemplified by that of a grass- 

 hopper. It is this, in part, which gives the bat so curious 

 and ungainly a gait ; and it is seldom that these creatures 

 are accurately drawn with the hind-leg in this seemingly 

 awkward but to them natural position ; a position which 

 results to a large extent no doubt from the fact that the 

 hind-limb is implicated in the organ of flight. And it is 

 one of the great structural advantages of birds over bats 

 and flying reptiles that the complete setting apart of the 

 wings for flight has left the legs free to become admirable 

 organs of progression on land. The position of the bat's 

 leg may be, however, to some extent a result of the 

 creature's habit of suspending itself by the claws of the 

 feet, since it prevents his continually knocking his knees 

 against the rock or stone surface on which he hangs sus- 

 pended in this way head-downwards. Most of us I suppose 

 have disturbed, in caves or old church towers, the poor 

 little flittermice in their winter sleep. At such times 

 breathing is almost suspended, the pulsations of the heart 

 fall from two hundred beats in a minute to thirty, the 

 blood is in a dark venous state, and the temperature of the 



