46 



DISSECTION OP THE DOG 



Except medially, the border circumscribing the base is sharp and fits into the 

 narrow space between the diaphragm and the ribs (sinus phrenico-costalis) . 

 It will be noticed that the two lungs differ in two conspicuous respects. 



(1) The incisura cardiaca is deeper in the right lung because the more bulky- 

 part of the heart, the base, inclines towards the right side of the body. 



(2) The right lung is the larger and possesses an extra (intermediate) lobe. 



(Esophagus 



Vena cava caudalis 



Fro. 19. — Diaphragmatic surface of the lungs. 



Dissection. — The constituents of the root of the lung should now be isolated. 

 In removing the pleura and the fatty connective tissue, great care should 

 be exercised not to injure the pulmonary plexus of nerves which is 

 cranial to the root. The plexus is more accessible on the left side, the 

 vena cava interfering with its dissection on the right. The various 

 structures should be followed into the interior of the lung, in order that 

 their manner of branching may be observed. 



Radix pulmonis. — The root of each lung contains the following structures : 

 (1) Several pulmonary veins conveying blood from the lung to the heart. 

 Although it is difficult to indicate the relative position of the root constituents 

 precisely without making the account of undue length, it may be said that, 



