AJffATOMT OF THE PIGEON. 535 



tine) is long and ends in a cloaca, which receives the ends 

 of the urinary canals and oviducts. Attention should be 

 given to the trachea ; its bronchial branches, the larynx and 

 t\ie syrinx or lower larynx, which may be developed either 

 at the end of the trachea, or at the junction of the trachea 

 and bronchi, or in the bronchi alone. The thymus gland 

 (Pig. 458, th) is very large and long, while the" thyroid {t) is 

 a small, oval mass situated at the beginning of the bronchi. 



The following account and drawings of the anatomy of 

 the pigeon have been prepared from original dissections by 

 Dr. 0. S. Minot. As pigeons are one of the most readily 

 obtainable and convenient types of birds, the following 

 description of the anatomy of a male is given as illustrative 

 of the class, those peculiarities being especially noticed by 

 which birds are distingaished from reptiles and mammals. 



Before dissecting a bird, it must be carefully plucked ; 

 this operation is much facilitated by dipping the animal in 

 boiling water for a few minutes. The limbs and muscles of 

 one, best of the left, side are to be removed ; the powerful 

 pectoral muscles cut off close to their attachment to the 

 keel of the breast-bone, and the ribs then cut away, care 

 being taken to avoid injuring any of the internal organs, 

 most of which will now be displayed in sHu nearly as shown 

 in Fig. 459, which represents a dissection carried somewhat 

 further. 



The skin (Fig. 459, E, from the neck) is characterized by 

 the presence of numerous ridges which cross one another, 

 so as to enclose quadrilateral spaces ; at the intersections 

 of the ridges are small pits in which the feathers are in- 

 serted. 



The digestive canal begins in the horny bill with three 

 openings, one the large gape or mouth, and two oblique 

 elongated nasal clefts (w), through which respiration is or- 

 dinarily alone effected. It then extends backward under- 

 neath the base of the skull, where it splits into the cesopha- 

 gus and trachea, two large tubes which run down the front 

 of the neck, the oesophagus on the right and the trachea 

 on the left. Just below the head the trachea lies, in its 

 normal position, in front of the oesophagus, though in most 



