308 ' ' FIELD ZOOLOGY. 



lished in 1829. The birds included represent the highest 

 type of physiological development among birds. 



With respect to the respiratory system, birds rival 

 man, having a more complicated system than does the 

 human animal. Some of the animals below the birds are 

 cold-blooded; the blood of some of them is oxygenated 

 only periodically; of others, only a portion of the blood 

 is aerated. In those animals where the blood is oxygen- 

 ated continuously, the consumption of food is most 

 rapid, and the temperature is highest. The body tem- 

 perature of man is ninety-eight and forty-six hundredths ; 

 but for birds, body temperatures range from one hundred 

 four to one hundred ten. Literally, these are the hot- 

 blooded animals. In the Passeres, the highest range 

 of the temperature is reached. Nothing could convince 

 one more fully of . these facts than one of these little, 

 nervous, frightened wild birds held in the hand. The 

 heart, pounding rapidly against the hand, seems about 

 to spill the life blood of the tiny feathered creature, as 

 the result of the extreme nervous tension under which it is 

 suffering. The Passeres consume the most oxygen and 

 live the fastest, that is, under the heaviest tax upon the 

 vital organs, of all the birds. 



The order is divided into two sub-orders on the 

 basis of the degree of development of musical apparatus 

 in the throat. In one sub-order, the Oscines, the musical 

 apparatus reaches a more or less high degree of perfection. 

 Several pairs of additional muscles are used in the pro- 

 duction of the sounds made by the bird, giving to the birds 

 forming this sub-order a range of musical ability not 

 equalled by the other orders. In the second sub-order, 

 the Clamatores, literally the crying birds, the musical 

 apparatus is not so highly developed. 



