XX.] THE STRUCTURE OF THE LUNO. 215 



appear only as a granular border lying 

 on the columnar cells. Goblet-cells will 

 probably be seen amongst the ciliated 

 cells. 



5. * Make longitudinal vertical sections of trachea, 

 taken through the tracheal rings, and compare 

 them with the transverse sections, noting es- 

 pecially the elastic and muscular elements. 



G. Take a piece of mammalian lung which has been 

 distended through the trachea with chromic 

 acid '2 p.c., and hardened in the same fluid (the 

 lung of a foetal or new-born animal serves best). 

 The chromic acid having been thoroughly ex- 

 tracted from it by alcohol (cp. p. 69 C, footnote) 

 place it in dilute haematoxylin for one to two 

 days so that it is deeply stained. Kemove it to 

 75 p.c. alcohol or to the fluid in which haema- 

 toxylin is dissolved (cp. Appendix) renewing the 

 alcohol as long as it becomes coloured, then place 

 for ten minutes or longer in strong spirit, and in 

 absolute alcohol. With blotting-paper remove 

 the excess of alcohol and transfer to bergamot 

 oil or oil of cloves for an hour or more. Then 

 remove the excess of oil and let the piece of lung 

 soak for two hours or more in just melted 

 paraffin or in a mixture of spermaceti (1 part) 

 and castor oil (4 parts). Imbed in the same 

 substance and prepare sections, using- olive oil to 

 wet the razor; treat the sections with creosote 

 and turpentine and mount then in Canada 

 balsam. Observe 



