26 Field Museum of Natural History — Zoology, Vol. XI. 



The Sense of Smell — The sense of smell is present in all mammals, with 

 the possible exception of the Toothed Whales. Branches of the 

 olfactory nerves are present in the upper portion of the nasal pass- 

 age, which come in contact with any odorous particles contained 

 in the air and which enter the nose. In many species this sense 

 is developed to a most extraordinary degree, warning them of 

 the approach of other animals at a surprisingly long distance. 

 Trappers have learned by experience that, if a trap is touched 

 with the bare hand, many species will not approach it for at 

 least 24 hours. 



The Sense of Hearing — The organ of hearing is present in all mammals, 

 but, as would be expected, is developed in some much more highly 

 than in others. It is divisible into three parts: i, external ear or 

 pinna and the auditory canal or meatus; 2, the middle ear or tym- 

 panum; 3, the internal ear or labyrinth. The pinna is present in 

 most mammals and is generally movably articulated to the skull, 

 and by muscular attachment enables the animal to turn it in the 

 proper direction to aid in collecting and directing the vibration of 

 sound into the meatus. While these ear muscles are present in the 

 ear of Man, from long disuse they are no longer functional except 

 in rare cases. The middle ear, drum of the ear, or tympanum, as it 

 is variously called, which forms the outer wall of the cavity, is 

 traversed by a chain of three or four movable small bones, three of 

 which are always present and are known, respectively, as malleus, 

 incus, and stapes. These bones are variable in size and character 

 in different mammals, especially in aquatic species. The malleus 

 in mammalian anatomy represents the quadrate bone of the lower 

 orders, which there connects the lower jaw with the skull. The 

 internal ear, or labyrinth as it is called, consists of three -semi-circular 

 canals, a vestibule and a cochlea. Here again is found, with the 

 exception of the Monotremes, a distinct mammalian character in 

 the spiral convolutions of the cochlea. By the vibrations of the 

 tympanic mem brane (produced by sound waves) and the small 

 bones, the vibrations of sound are transmitted from the exterior to 

 the fluid filling the internal ear and are appreciated by the end 

 filaments of the auditory nerve, thus enabling the animal to hear. 



The Sense of Taste — The sense of taste concerns us little here and 

 will be dismissed with the brief statement that it is chiefly located 

 in the papilla on the dorsal surface of the tongue, although 

 similar papillae are present in other parts of the mouth, such as 

 the soft palate, epiglottis, etc. These papillae are each furnished 

 with a branch of the glossopharyngeal nerve. 



