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Practical Zoology. 



(a) the conical shape of the whole ; compare this with the chest 

 cavity, as shown in a skeleton ; (^) how the lungs nearly sur- 

 round the heart ; (V) the concave posterior surface of the lungs 

 where they fitted the convex anterior surface of the diaphragm ; 

 (d) the groove between the dorsal surfaces of the lungs in which 

 the spinal column fitted ; (<?) the smooth, undivided dorsal 

 surface of the lungs, and their division ventrally into lobes; 

 (/) the relative lengths of the dorsal and ventral surfaces of 

 the lungs. The anterior end of the lung is the apex ; the 

 posterior end is the base. Open the valve of the faucet. 

 What makes the air go out? Again inflate. Does it require 

 effort to do so ? Why ? Cut off the end of one lobe and again 

 inflate. Does the air escape ? Throw a piece of lung on water. 

 Pinch a piece of lung, holding it near the ear. The smooth, 

 moist, glistening membrane covering the lung is the pleura. 



5. Observe a large whitish or yellowish tube running in the 

 groove between the dorsal surfaces of the two lungs. It is 

 usually covered with fat. It may have been cut off short, so that 

 its open end is easily seen near the windpipe. This is the main 

 artery, the aorta. Take hold of its free end and separate it 

 from its attachment to the other tissues, cutting close to it with 

 the scissors, so far as where it arches over the root of the left 

 lung. Now turn the free end forward. 



6. Find where the gullet is cut off posteriorly ; slit it open for 

 an inch or two, and note its whitish lining, the mucous coat. 

 The thick red coat is the muscular coat ; it has an inner layer of 

 circularly arranged muscular fibers and an outer longitudinal 

 layer. Beginning posteriorly, separate the gullet from the wind- 

 pipe, cut off the windpipe about the middle, and entirely remove 

 the gullet and larynx. 



7. Examine the windpipe ; insert a finger, and stretch it ; note 

 its C-shaped cartilages. Its lining is a mucous membrane. 



8. Lay the heart and lungs on their ventral surface, with the 

 posterior end near you. Using the handle of the scalpel as a 

 chisel, clear away any tissue covering the windpipe, and trace it 



