126 CHEIROPTERA. 



brain were reeling from the effects of disease. It steers a very deviating 

 course, falling lirst to one side and then to the other, as it employs the 

 limbs of either side. 



In their general form the Cheiroptera resemble the Quadrumana, and 

 like the latter the female has two teats. Their internal structure is pecu- 

 liar, the skeleton is slightly but strongly built, the bones never have air- 

 cavities as birds have, the vertebrae are broad and short, the ribs long, 

 the legs very slender, the collar-bone and shoulder-blades thick and 

 strong. The extraordinary development of the skin makes these crea- 

 tures look larger than they really are, and in some species its immense 

 growth in the nose and ears gives them their peculiarly repulsive look. 



All the Cheiroptera sleep by da)-. They suspend themselves head 

 downwards by the hind feet, frequently clinging to each other in compact 

 masses. 



In cold and temperate regions bats iiibernate. They are then abso- 

 lutely insensible, and may be handled, shaken, and even thrown in the 

 air, without betraying the least movement. But if they are held for 

 some time in the hands, or near a fire, under the influence of the heat 

 they rapidly show signs of animation. 



During the period of torpidity the vital functions are executed 

 feebly, but the}- are not altogether abolished. They cannot dispense 

 with nourishment during this portion of their existence, but as they 

 are incapable of taking food, they devour their own substance, the fat 

 that has accumulated in their bodies during the period of activity. In 

 this way is explained their emaciation at the termination of their winter 

 sleep. 



Professor Owen writes: "The preservation of life in tliis passive 

 state is due to the irritable property of the fibre of the heart, which is 

 excited to contract by the blood in its carbonized state. The slow cir- 

 culation of venous blood is the only recognizable vital act during hiber- 

 nation, and the material convej'cd by the absorbents is sufficient to 

 counterbalance the slight waste. The bat is thus independent of sup- 

 plies from without, but it purchases that independence by a temporary 

 abrogation of its vital functions. Cold, senseless, motionless and asphyxi- 

 ated, its entry into death's chamber is prevented only by its being 

 brought to his verj^ door." 



Bats usually have only one offspring at a time. As soon as brought 

 forth, the mother carefully cleans it, envelops it in her wings as in a 



