380 



DR. R. W. SHUFELDt's MORPHOLOGICAL 



The Heart and Carotids, Trachea, Viscera, Sfc. 



Cypseli as a rule possess but a single carotid, the left one ; 

 Professor Garrod, however, discovered that Cypseloides proved 

 an exception to this. In Ghcetura I found but one, which was 

 disposed along the anterior aspect o£ the neck in the most usual 

 manner; while in Micropus melanoleuciis the left carotid, here 

 also the only one present, takes on a peculiar course, for being 

 so far over to the left, it passes up to the front of the neck 

 obliquely, and completely outside the protection of the muscles 

 and the hypophysial canal of the vertebrae. 



Past the middle point of the neck, however, it enters between 

 the muscles to the aforesaid canal, and then follows the usual 

 course to the head. 



Swifts do not possess a heart of any unusual dimensions ; but 

 Humming-birds, on the other hand, have a heart quite as unpro- 

 portionately large for their size as are the feet of these, the other- 

 wise pygmies of the Class. They too have but one carotid, so 

 fa]* as I have examined, the left one alone being represented. 



MacGrillivray, in Audubon's ' Birds of North America,' under 

 the latter's account of Trochilus colubris, presents us with a very 

 good description of the trachea in a Humming-bird. He says of 

 it that " The trachea is 9 twelfths long, being thus remarkably 

 short on account of its bifurcating very high on the neck, for if it 

 were to divide at the usual place, or just anteriorly to the base of 

 the heart, it would be 4i twelfths longer. In this respect it differs 

 from that of all other birds examined, with the exception of the 

 Roseate Spoonbill {Flatalea ajaja), the trachea of which is in so 

 far similar. The bronchi are exactly | inch in length. Until 

 the bifurcation, the trachea passes along the right side, after- 

 wards directly in front. There are 50 rings to the fork ; and 

 each bronchus has 31^ rings. The breadth of the trachea at the 

 upper part is scarcely more than | twelfth, and at the lower part 

 considerably less. It is much flattened, and the rings are very 

 narrow, cartilaginous, and placed widely apart. The bronchial 

 rings are similar, and differ from those of most birds in being 

 complete. The two bronchi lie in contact for 2 twelfths at the 

 upper part, being connected by a common membrane. The lateral 

 muscles are extremely slender. The last ring of the trachea is 

 four times the breadth of the rest, and has on each side a large 

 but not very prominent mass of muscular fibres, inserted into the 

 first bronchial ring. This mass does not seem to be divisible 



