30 PRACTICAL PHYSIOLOGY 



work between their fibres and to the presence of myohaematin in the 

 fibres themselves ; physiologically they are far less readily fatigued and 

 show a contraction four or more times as long as that of the white 

 gastrocnemius (Fig. 35). 



For comparison with the single twitch of the gastrocnemius, that 

 given by the hyoglossus may now be studied. This muscle, arising 

 from the anterior edge of the body of the hyoid cartilage, runs forwards 

 into the substance of the tongue. 



A Hyoglossus Preparation is made by cutting off the whole of 

 the lower jaw, including the tongue and hyoid cartilage. Place it 

 on the myograph board, mucous surface upwards, turn the tongue 



Fio. 35. Comparison of contractions of red and white muscle of rabbit, stimulated 

 indirectly. Upper curve is response of the red soleus and lower curve that of the 

 white gastrocnemius. Time marker, 50 per sec. The tracing to be read from right to 

 left. (M.S.P.) 



forwards, and connect its tip to the lever by a thread. Firmly fix the 

 hyoid cartilage by running a pin through it into the cork. Two needle 

 electrodes transfix the base of the muscle just in front of the hyoid. 



All the other connections are the same as when studying the single 

 contraction of the gastrocnemius; a weight of 5 or 10 grams is placed 

 near the axis of the lever. 



Compared with the single twitch of the gastrocnemius, that given by 

 the hyoglossus (Fig. 36) shows the following differences : the whole 

 contraction lasts more than twice as long, the latent period is slightly 

 longer, but it is the period of shortening and still more that of relaxa- 

 tion which is more gradual and prolonged. 



Action of Veratrine. A brainless frog is poisoned by injecting into 

 the dorsal lymph sac 5 minims of a saturated (1 in 1000) solution 

 of veratrine in normal tap-water saline. In order that the drug may 



