300 



PRACTICAL HISTOLOGY. 



[XXVII. 



8. Fresh Lung. Tease a small piece of lung in normal saline. 

 It is difficult to get rid of all the air, but this may be done by 

 beating the tissue with a needle. 



(H) Observe the large number of fine elastic fibres, which 

 branch and anastomose. They can be rendered more evident by 

 running in dilute caustic potash (2 percent.) under the cover. This 



destroys to a large extent the other 

 elements. 



9. Dried Lung. (i.) With a dry 

 razor make thin sections of a dried 

 and distended lung. Examine the 

 section in water, taking care that 

 it does not curl up, which it readily 

 does. Get rid of the air-bubbles by 

 pressing on the section with a needle, 

 (ii.) Make rather thick sections 

 parallel to the pleura, and examine 

 them by reflected light. A very good 

 idea of the air-vesicles is thus ob- 

 tained. 



(a.) (L) Observe the air-vesicles, 

 and the thin partitions between them. Also sections of the 

 infundibula or alveolar passages. Connective-tissue septa may 

 be seen. Of course the finer details of structure cannot be made 

 out (fig. 290). 



10. Foetal Lung. This serves very well for showing that a lung 



FIG. 290. T.S. Dried Lung. a. Vesi- 

 cles ; 1. Infundibula. 



FIG. 291. T.S. Foetal Lung, showing a Bronchus Terminating in Air- Vesicles, x 75 

 B. Epithelium lining an alveolus, x 300. Miiller's fluid and hwmatoxylin. 



is made up of lobules. Harden in Miiller's fluid (14 days) the 

 lungs from a human foetus (12 cm. in length). Cut sections and 



