20 THE HISTORY OF ANIMALS. [B. I. 



mouth ; by the epiglottis the passage of the tongue is closed, 

 at the other extremity the trachea reaches to the middle 

 of the lungs, and afterwards divides to each side of the lungs. 

 For the lung is double in all animals which possess this 

 part, though the division is not so marked in viviparous ani- 

 mals, and least of all in man. The human lungs are ano- 

 malous, neither being divided into many lobes, as in other 

 animals, nor being smooth. 



7. In oviparous animals, such as birds and the oviparous 

 quadrupeds, the parts are very widely separated, so that 

 they appear to have two lungs ; they are, however, only two 

 divisions of the trachea extending to each side of the lungs ; 

 the trachea is also united with the great vein and with the 

 part called the aorta. When the trachea is filled with air, 

 it distributes the breath into the cavities of the lungs, which 

 have cartilaginous interstices ending in a point ; the passages 

 of these interstices go through the whole lungs, always divid- 

 ing from greater into less. 



8. The heart is connected with the trachea by fatty and car- t 

 tilaginous muscular bands. There is a cavity near the junction, 

 and in some animals, when the trachea is filled with breath, 

 this cavity is not always distinguishable, but in larger ani- 

 mals it is evident that the breath enters it. This then is the 

 form of the trachea, which only inhales and exhales breath, 

 and nothing else either dry or moist, or it suffers pain till that 

 which has passed down is coughed up. 



9. The oesophagus is joined to the mouth from above, near 

 the trachea, being united both to the spine and the trachea 

 by membranaceous ligaments. It passes through the dia- 

 phragm into the cavity of the stomach, is fleshy in its nature, 

 and is extensible both in length and breadth. The human 

 stomach is like that of a dog, not a great deal larger than the 

 entrail, but like a wide bowel ; after this there is an entrail 

 simply rolled together, then an entrail of moderate width. 

 The lower part of the abdomen is like that of a hog, for it is 

 wide, and from this to the seat it is short and thick. 



10. The omentum is united to the abdomen in the middle, 

 and is in its nature a fatty membrane, as in other animals 

 with a single stomach and teeth in both jaws. The mesente- 

 rium is over the bowels ; it is membranaceous, broad, and fat ; 

 it is united to the great vein and the aorta : through it extend 



