v - RESPIRATION 45 



is bounded below by the diaphragm, a large dome- 

 shaped muscle that divides the body into two parts, 

 called the chest and the abdomen, and above by the 

 muscles of the neck. 



The healthy lungs of a young person have a pale 

 pinkish color, while the lungs of an old man who has 

 lived many years in a city full of dust and smoke have 

 a dark brown, almost black, color. 



FIG. 18. Front view of the lungs, heart, and large blood vessels (Zuppke). 



The right lung is a trifle larger than the left, weighing 

 about two ounces more. Each lung is composed of 

 parts or divisions called lobes. The right has three 

 lobes and the left two. The lobes in turn are made up 

 of numerous small lobules. Did you ever notice the 

 peculiar mottled appearance of a fresh lung ? Each 

 of the little areas is a lobule. If we look at a lobule 

 under the microscope, we shall see that it consists of 

 bunches of sacs rilled with air and capillaries filled with 



