THE HUMMING BIRDS. 293 



Gannet, a bird of moderately slow stroke, makes ordinarily one hundred and fifty 

 strokes a minute, and that judging from the appearance of a small wheel driven at 

 the rate of a thousand revolutions a minute the wings of a Humming Bird make not 

 far from five hundred vibrations in the same short space of time. 



So great an exercise of muscular power as that involved in such rapid movements 

 necessarily causes rapid waste of tissue and calls for an ample supply of blood, and 

 we find that this is provided for by a remarkable large heart.* 



The actual speed of the Humming Bird is less than the ordinary observer might 

 suspect, for the small size of the creature adds to the seeming rapidity of its flight, 

 just as the little puffing tug appears to move faster than the ferryboat, although it 

 really does not do so. 



The wing and flight of a Humming Bird are comparable to the wing and flight of 

 a fly, or, better still, a Hawk Moth, both possessing a rigid wing driven at a high 

 rate of speed, and both possessing the ability to hang suspended in the air or to 

 dart erratically about in a manner that defies the eye to follow. 



Eapidity in the stroke of the wiug is gained by shortening the upper arm bones, 

 the bones of the hand on the contrary being lengthened to support the shafts of the 

 large primaries. The inner portion of the wing is furthermore shortened, and speed 

 consequently gained, by flexing the forearm, and examination of a bird in the flesh 

 will show that it is quite impossible for a Humming Bird to extend its wings as do 

 other birds. 



The wing of a bird is a lever of the third order, and since the power is applied at 

 a disadvantage, any increase of speed calls for corresponding increase in driving 

 power, which in a bird means larger pectoral muscles and a larger breastbone. Now 

 the sternum of a Humming Bird is, relatively to the size of the bird, by far the 

 largest in the entire class of birds, and although the proportion of length to depth 

 of keel is equaled in some Swifts, it must be remembered that the sternum of a Hum- 

 ming Bird is not only deep, but long, running nearly the entire length of the body. 

 The increased size of the pectoral muscles not only adds to the power of flight, but 

 to the stability of the bird, for the weight, like the ballast of a cutter yacht, is thus 

 brought low down. 



All attachments to the wing muscles are large, and when the humerus is magni- 

 fied to the size of that of a Swift it is seen to be the more rugose of the two. At 

 first sight the breastbone might appear too thin to resist the strain of the muscles 

 it supports, but these being arranged in pairs pull as it were one against the other, 

 thus relieving the sternum of the strain that would otherwise be brought upon it. 



In short, the Humming Bird is a piece of mechanism most admirably adapted for 

 flight, and wonderful as are the modifications of plumage in various members of the 

 group, no less remarkable is the adaptation of the skeleton for the most rapid and 

 remarkable aerial maneuvers. 



Description of the tongue. — The tongue of the Humming Bird, like that of the 

 Woodpecker, is extremely loug, but the two differ decidedly in their structure, and 

 the muscles by which the tongue is protruded and retracted are applied in a totally 

 different manner in the two birds. 



The free portion of the tongue is divided for about half its length, and when with- 

 drawn lies just within the lower mandible. Toward the base it consists of a some- 

 what flattened tube of dense cartilage, grooved along the center above and below, 

 and with a slighter groove on the upper exterior surface. This single tube divides 

 before reaching the forked part of the tongue, and a flange is developed along the 

 outer edge. This flange, or border, becomes membraneous, and seems to curl up- 

 ward and inward, converting the forked tip into two tubes or gutters. That these 



* According to Mr. G. Gulliver (in Proceedings of the Zoological Society of Loudon, 

 1846, p. 28), the blood-corpuscles of a Humming Bird (species not stated) measure 

 ?Ft>tf °y ToW °f an inch, the long diameter of the nucleus being very nearly Tinfo of an 

 inch; the temperature of the blood about 105°. — R. R. 



