6 ELEMENTARY ZOOLOGY 



the opposite extremity is the posterior end. In most 

 animals we note two other views or aspects ; that which 

 is called the "back" and with most animals is, under 

 ordinary conditions, uppermost is the dor sum or dorsal 

 aspect, while that which lies below is the venter or ventral 

 aspect. When referring to a view from one side we speak 

 of it as a right or left lateral aspect. These terms hold 

 good for most of the animals that we shall study. 



Note at the anterior end of the toad a wide transverse 

 slit, the mouth. What other openings are on the anterior 

 end ? Note the two large eyes, the organs of sight. Just 

 back of each eye note an elliptical, smooth membrane. 

 This is the tympanum of the outer ear, and through this 

 membrane the vibrations produced by sound-waves are 

 transferred to the inner ear, which receives sensations and 

 transmits them to the brain. Open the mouth by drawing 

 down the lower jaw. Note just within the angle of the 

 lower jaw the tongue. How is it attached to the wall of 

 the mouth ? On the tongue are a great many fine papilla 

 in which is located the sense of taste. It has now been 

 seen that most of the special senses of the toad have their 

 seat in the head. Pass a straw or bristle into one of the 

 nostrils. Where does it come out ? These internal 

 openings to the nose are the inner nares. Note in the 

 roof of the mouth just posterior to each of the eyeballs an 

 opening. These are the internal openings to the wide 

 Eustachian tubes, which lead to the mouth from the 

 chamber of the ear behind the tympanum. 



Note far back in the mouth an opening through which 

 food passes. This is the oesophagus or gullet. Note just 

 below this gullet an elevation in which is a perpendicular 

 slit, the glottis. This is the upper end of the laryngo- 

 tracheal chamber, and the flaps within on either side of 

 the slit are the vocal cords. 



Note at the posterior end of the body in the median 



