82 ELEMENTARY PHYSIOLOGY. [VIII. 



cells may also be seen carried about by the 

 action of their own cilia. 



d. The contracted, almost globular form of the 

 cells which have been set free. 



3. Tear off the smallest possible strip of a frog's 

 muscle, which has been kept extended and 

 preserved in alcohol, and tease it out as finely as 

 possible in dilute glycerine. Note 



a. The varying size of the fibres. 



1). The striation of the fibres : alternate dim and 

 bright cross-bands passing through the whole 

 thickness of the fibre. 



c. The breaking up of the fibre into fibrillse, 

 the latter also striated. Try to obtain as 

 fine fibrillse as possible. The fibres sometimes 

 split transversely into discs ; this is usually 

 the case when the muscle has been preserved 

 in picric acid ; the surfaces of the discs ap- 

 pear dotted. 



4. Cut through the skin of the front of the thigh 

 of the frog used in 2, note the sartorius muscle 

 running somewhat obliquely across the thigh 

 from top to bottom, seize with forceps the con- 

 nective tissue lying along its inner border in the 

 upper part of the thigh and tear this back to 

 the knee, remove similarly the connective tissue 

 at its outer border, thus the tissue covering the 

 muscle will also be removed. Take up with fine 

 forceps a few fibres at one end of the muscle, and 



