INTRODUCTION. 55 



in the air during flight. As in other ruminants incisors are 

 deficient in the upper jaw_, being there replaced by a dental 

 pad, and in the inferior maxilla the canines assume the 

 figure of incisors and form part of a continuous series of 

 eight. 



The anterior extremities of the nasal and oral chambers 

 are connected together by a duct of Stenson, leading to 

 the organ of Jacobson, an accessory olfactory appa- 

 ratus, in all probability closely connected with the mouth 

 that the sense of smell may exercise more direct control 

 against ingestion of poisonous herbs. The upper lip and 

 the anterior nares are occupied by the muffle, a fibrous 

 organ covered with a delicate but firm membrane devoid 

 of hair, but constantly, in health, secreting a dewy moisture, 

 and kept clean by the tongue, an organ developed to a 

 remarkable extent for prehensile purposes. The eyes are 

 prominent and rather far back as in other herbivores, 

 whereby extensive range of vision enables the animal to 

 view an enemy afar and not be disturbed suddenly during 

 the prolonged period of rumination. This act is performed 

 by the animal in the recumbent position, the rumen is full 

 and presses against the diaphragm. 



The thorax, under any circumstances, is not remarkable 

 for extent, but has special provisions whereby it may in- 

 crease in transverse diameter when the animal is lying 

 down. Besides the shortness of the thorax of the ox and 

 other ruminants as compared with that of the horse and 

 his allies, the lungs are more largely composed of areolar 

 tissue, the calibre of the trachea is less, and the anterior 

 nares are smaller and less mobile, and devoid of that 

 remarkable complexity of formation which assists in 

 adapting the horse for rapid movement over the earth. 

 Altogether the respiratory system is less developed than 

 in the horse. 



In accordance with this the circulatory system is less 

 developed, the arteries being small and the heart generally 

 more frequent but less powerful in its action, so that the 

 pulse has a somewhat soft beat. The blood does not ex- 

 hibit that tendency to the formation of the buffy coat 



