460 



RESPIRATION, 



kfj X 



Fig. 128 (WATERS) Represents a very thin slice of a cat's lung (injected, inflated, 

 and dried), from the surface of the lung. The eye is looking upon the cut surface. 

 The depressions, a a, are the bottoms of the air sacs, resting on the pleura. The light 

 coloured lines that surround them are their walls, and the small depressions seen within 

 the walls, b b, marked off by less distinct lines, are the alveoli. The specimen from 

 which this drawing was made was a very good one, and the drawing may be considered 

 as fairly representing the appearance presented. 



Fig. 129 (WATERS) Represents a thin slice of a cat's lung, viewed in the same way 

 as in the last two drawings, a a, are the air sacs, and b b, the alveoli, situated at 

 their fundus. The dark lines are the walls of the air sacs and alveoli. This drawing 

 was made from a reflection of the object by means of a camera lucida fixed to a micro- 

 scope : the outline of the walls of the aix sacs and of the alveoli was traced as it was 

 thrown on paper. 



