56 ELEMENTARY PHYSIOLOGY. [IV. 



7. Take a piece of cartilage from the head of a 

 cuttle fish which has been preserved in picric acid 

 and subsequently in alcohol. Cut sections, im- 

 bedding if necessary (Lesson vi. 1). Select a 

 thin section and immerse it in hsematoxylin for 

 a few minutes watching that it does not stain 

 too deeply, place it in a watch-glass containing 

 spirit to remove the colouring matter simply ad- 

 hering to the tissue (if it is too deeply stained, 

 place it in a little 1 p.c. acetic acid and when it 

 is sufficiently decolourised, replace it in the 

 spirit), then mount it in glycerine. Observe 



a. The groups of cartilage cells. 



b. The marked processes proceeding from the 

 cells of one group, running towards and 

 anastomosing with the processes from the 

 cells of other groups. 



8. Take a small piece of the ear of a freshly killed 

 mouse or young rat, remove the skin and scrape 

 away the tissue surrounding the ear-cartilage. 

 Mount the cartilage in normal saline solution. 

 Observe that the cavities of the cells, generally 

 polygonal in form, are separated by very narrow 

 partitions of matrix. From many of the cavities 

 the corpuscles have disappeared altogether, 

 leaving simply a honeycombed matrix. This 



probably spoil the section ; on the other hand if the glycerine spreads 

 beyond the cover-slip the balsam will not stick to the glass, in this 

 case it is generally less trouble to remount the specimen than to wipe 

 away the superfluous glycerine. The Student should make one or 

 two trials to find out the proper quantity of glycerine to take with the 

 cover- slips he uses. 



