164 HUMAN LUNG: RED CORPUSCLES 



The tiniest openings, of which many hun- 

 dreds are visible, are the lung alveoli, or air 

 cells. It is in these that the blood is aerated. 

 Their walls are comprised of a network of 

 blood vessels. 



The original photo-micrograph (Fig. 50) 

 showed an amplification of 20 diameters ; the 

 focal distance was 60 inches ; and the objec- 

 tive used was the 3-inch. 



Red Corpuscles. 



Although to the naked eye the blood seems 

 uniformly tinted, it is found by the microscope 

 to be really an almost colourless fluid, con- 

 taining minute coloured cells which contain the 

 haemoglobin or red colouring matter of the 

 blood. Even in thin layers the blood is opaque, 

 on account of the different refractive powers of 

 the corpuscles and the plasma in which they 

 are suspended. 



In man, and in all mammals except the 

 Camelidse, the form of the coloured corpuscles 

 is that of a bi-concave disc. In the Came- 



