LESSON VIII. CILIA. AXON REFLEX, 

 RHEOSCOPIC FROG. 



1. Cilia. Place a pithed frog on its back, cut through 

 the lower jaw in the middle line, and carry the incision 

 down the oesophagus as far as 'the stomach. Pin back 

 the parts divided, and moisten the mucous membrane, 

 if it is at all dry, with normal saline solution. Place 

 across it in a line, as high up as practicable, three small 

 thin pieces of cork. The pieces of cork will be seen to be 

 driven by ciliary action towards the stomach; probably 

 the middle piece will travel the fastest. Warm saline 

 solution will increase the ciliary activity. 



2. Axon reflex in nerves to muscle. The nerve 

 fibres supplying a muscle divide into several branches and 

 the branches supply separate muscle fibres. If any one 

 branch is stimulated, the nervous impulse spreads over 

 all the branches, and causes contraction in several 

 muscle fibres. In some muscles which are divided into 

 two or more segments by tendinous insertions, some of 

 the nerve fibres send branches to two adjoining segments 

 and in consequence stimulation of certain parts of one 

 segment will cause contraction in the adjoining segment. 

 This can be shown in the gracilis major of the frog (cp. 

 Fig. 6). 



Expose the gracilis major on one side, place a crystal 

 of NaCl a little below the tendinous insertion ; in a short 

 time there will be twitchings of the muscle fibres near 

 the salt and some twitchings in the muscle on the oppo- 

 site side of the tendon. 



