388 



zooLoor 



brane, and lastly a hard, white shell. Two of these eggs are laid, 

 one after the other, in successive days, and then incubated by 

 the parents, who l:)y sitting on them maintain them at the tem- 

 perature of the body, so that the egg develops. After fourteen 

 days the young pigeon hatches and is fed and brooded by the 

 parents for a time longer until it is able to care for itself. 



The muscular system is best developed in connection with 

 the function of flight. Every one who has eaten a chicken or 



'IV / ; 



^vnini 



Fig. .3.5G. — The brain of the pigeon, left side : o?/, olfactor>' lobe : ch, 

 cerebral hemispheres; pn, pineal body; ch, cerebellum «-ith a side lobe 

 at /; ot, optic tract; >iio. medulla oblongata: 1-XlI, cranial ncr-\-es ; 

 sp.I, spinal nerve. From Parker's "Zootomy." 



turkey knows of the great " breast " muscles. These consti- 

 tute " white " meat in the turkey because they are relatively 

 bloodless, being little used for flying ; but in pigeons, which 

 fly readily, the breast muscles are full of blood and are dark. 

 The great breast muscles depress the ■^^^ng, the reaction to 

 which keeps the bird in the air. The other muscles of the 

 body are less important. Those of the neck and tail are well 

 developed, corresponding to the mobility of these parts, but, 

 owing to the compact, immobile nature of the trunk proper, the 

 musculature of that region is very slight. 



