190 PRACTICAL HISTOLOGY [XXIV 



tion). The close capillary network occupying almost all the 

 space between the nuclear groups. The blood-corpuscles in the 

 capillaries (alcohol specimen), stained orange with eosin ; focus 

 up and down and note how near the surface the corpuscles are. 



The capillary network may be made obvious and the outlines 

 of its constituent cells shown, by injecting the vessels with silver 

 nitrate (cp. Lesson xvn. 5). 



6. Distend the lungs of a pithed newt (or frog) with 30 p.c. 

 alcohol ; leave the lung in this fluid for two days, wash, place for 

 a day in Ranvier's picrocarmine ; wash, place in dilute glycerine. 

 Scrape the inner surface, and tease the scrapings in dilute 

 glycerine. Observe 



The isolated lining cells of the lung, consisting of a thin 

 hyaline ground plate, having near one border a nucleus with a 

 little granular cell substance around it. 



DEMONSTRATIONS. 



1. Longitudinal and transverse sections of trachea 

 (cat), stained with orcein. Note the band of elastic 

 fibres in the mucous coat, and the scattered elastic 

 fibres in the fibrous coat. 



2. Section of lung, stained with orcein. Note the 

 considerable amount of elastic tissue in all the tubes as 

 far as, and including, the openings of the alveoli, and 

 the network of fine fibres in the thin walls of the 

 alveoli. 



3. Section of lung of foetal mammal. Note in the 

 alveoli the absence of large flat cells. 



4. Inner surface of frog's lung (distended and 

 fixed with alcohol). Observe with the unaided eye, 

 and with a lens, (a) the large central space, (6) the 



