270 



Hitchcock's anatomy 



COMPARATIVE PNEUMONOLOGY. 



RESPIRATORY ORGANS. 



481. Trachea. — The Trachea in some animals, such as the 

 horse and cow, consists of complete rings, while in many ani- 

 mals they are only portions of rings, whose free extremities 

 are united by membrane. In man these rings number from 

 seventeen to twenty, in the whale from seven to twelve, in 

 the carnivora from thirty to forty, and in some camels one 

 hundred and ten. 



482. Bronchi. — The Bronchial Tubes are usually two in 

 number, but in the ruminants, the dolphins, and some other 

 mammals there are three. This third tube is always the 

 smallest, and passes to the right lung. 



483. Lungs, — In the horse the lungs are undivided, but 

 in most quadrupeds the number of lobes is greater than in 

 man. In the marmot and hamster there are five in the right, 

 and three or four in the left lung. In the musk deer the 

 right lung is nearly twice the size of the left. The terminal 

 air-cells of all these animals correspond in size very nearly 

 with those of man. The lungs are proportionally the largest 

 in the more powerful carnivora, and smallest in the weak 

 herbivora, and the red blood corpuscles are much more abund- 

 ant in the blood of the former than of the latter. 



484. Respiration of Birds. Lnnglets.— In Birds the 



respiratory apparatus, like that of Insects, extends through a 

 large part of the body, (Fig. 264, p. 271), not only in tho 

 lungs proper, but through the channeled bones which are lined 

 W T ith a membrane for purifying the blood. (Fig. 265, p. 271.) 



481. How does the trachea in many of the lower animals differ from that of man? 

 What is the relative number of rings in each ? 4S2. What is said of the number of the 

 principal bronchial tubes ? 483. What of the number of lobes in many quadrupeds? In 

 what animals are the lungs largest and in what ones weakest? 484. How is the respir- 

 atory apparatus of birds and insects alike ? 



