RESPIRATION. 



_ Fig. 69. 



235 



Fig. 70. 



HUMAN LARYNX, TRACHEA, BRONCHI, AND LUNGS; showing the ramification of the 

 bronchi, and the division of the lungs into lobules. 



vascular membrane inclosing a cavity; which cavity is divided 

 into a large number of secondary compartments by thin septa or 

 partitions, which project from its internal surface. (Fig. 70.) These 

 secondary cavities are the "pulmonary 

 cells," or " vesicles." Each vesicle is about 

 7*5 of an inch in diameter ; and is covered 

 on its exterior with a close network of ca- 

 pillary bloodvessels, which dip down into 

 the spaces between the adjacent vesicles, and 

 expose in this way a double surface to the 

 air which is contained in their cavities. 

 Between the vesicles, and in the interstices 

 between the lobules, there is a large quan- 

 tity of yellow elastic tissue, which gives 

 firmness and resiliency to the pulmonary 

 structure. The pulmonary vesicles, accord- 



.-, i , n T7-.-1T1 SlNGT.ELOBCLEOFHu- 



ing to the observations of Kolhker, are MAMLlJNG ._a. ultimate bn> n - 

 lined everywhere with a layer of pa3einent chial tube - 6 - cavitv of icbnie. 



J . c,c,c. Pulmonary cells, or vest- 



epithelium, continuous with that in the c ies. 



