LESSON VIII. 



STRUCTURE OF CONTRACTILE TISSUES. 



1. Cut off the head of a frog which has just been 

 killed, remove carefully the lower jaw and upon 

 the mucous membrane of the roof of the mouth 

 pour a little osmic acid 1 p.c. (before doing this 

 a small piece of the membrane may be cut out 

 to serve for § 2). Cover up the preparation and 

 leave it for about half an hour' then scrape a 

 small area of the mucous membrane and tease 

 out the flakes so obtained in water or in dilute 

 glycerine, putting a small piece of paper under- 

 neath the cover-slip to avoid pressure. Examine 

 under a high power. Groups of ciliated cells 

 intermingled with mucous (goblet) cells will be 

 seen; neglect the latter, note in the former 

 a. The shape of the cell varies, it often branches 

 irregularly at its attached end. 



' Or the imioous membrane after treatment with osmic acid as 

 above may be gently washed with water to get rid of the fumes of the 

 aeid, removed with forceps and scissors, pinned out with hedgehog 

 quills and placed in osmic acid 1 p.c. for 1 to 24 hours as convenient. 

 The oesophagus and the mucous membrane of the floor of the mouth 

 which also have cilia may be similarly treated. 



