156 Practical Zoology. 



Drag out the vitreous humor and note the soft whitish or 

 pinkish retina ; observe that it is a continuation of the optic 

 nerve. Tear away the retina, noting its consistency. Note the 

 color and luster of the inner surface of the choroid coat. The 

 dark layer on the inside of the choroid coat is the pigment layer 

 (outer part) of the retina, which adheres to the choroid, and is 

 torn loose from the rest of the retina. 



The reflection of light from this surface of the choroid coat 

 causes the color seen in the eyes of some animals. Turn the 

 remaining coats inside out, and tear the choroid coat from the 

 sclerotic. Observe the blood tubes passing from one to the other. 



DISSECTION OF THE LARYNX. 



The Larynx of the Calf. (As the larynx of the rabbit is so 

 small, it will be better to examine a larger one.) i. The front 

 of the larynx is readily distinguished by the projection of cartilage 

 known as the Adam's apple. 



2. Along the back of the larynx runs a thick, muscular tube, the 

 gullet, with a whitish lining, the mucous membrane. 



3. Trim away the muscles and other tissues from the front and 

 sides of the larynx. The large cartilage forming the greater part 

 of the front of the larynx is the thyroid cartilage. 



4. Observe the band of muscles attached to either side of 

 the thyroid cartilage and passing horizontally back around the 

 gullet or esophagus. 



Cut away this muscle as completely as possible, and entirely 

 remove the gullet. Note that the whitish or yellowish mucous 

 membrane which lines the gullet is continuous with the lining 

 of the larynx. Study now more fully the shape of the thyroid 

 cartilage. 



5. Back of the upper part of the thyroid cartilage, covering 

 the upper end of the larynx, is the arched epiglottis. Feel of 

 it to learn its consistency. Press it upward and forward, then 

 downward and backward ; observe that it now covers the entrance 

 to the larynx ; note the position it takes when released. 



