68 PRACTICAL HISTOLOGY [iX 



b. Mount in dilute glycerine, and examine the 

 section which has been treated with osmic acid ; the 

 fat globules are stained a deep brown-black, the cell 

 substance, the nuclei and the matrix are but slightly 

 stained. On keeping, the fat globules become black. 



5. Sections of cartilage from the head of a cuttle-fish (picric 

 acid) 1 . Stain a section with acid hsomatoxylin, wash it, and 

 mount in glycerine. If it is too deeply stained, place it in a 

 little 1 p.c. acetic acid and when it is -sufficiently decolourized, 

 wash out the acid. Observe 



a. The groups of cartilage cells. 



b. The marked processes proceeding from some 

 of the cells. Sometimes the processes of neighbouring 

 groups may be seen to join. 



6. 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. 



Note the cartilage cells closely packed together, most have 

 one or more refractive fat globules in them. (The fat increases 

 up to a certain limit with the age of the animal.) Unmount, 

 stain the specimens with osmic acid. 



1 Picric acid, osmic acid, and mercuric chloride are all good 

 fixing agents for hyaline cartilage. 



