INFLUENCE OF VERATEINE 49 



This is better seen in fig. 52, obtained from a gastrocnemius, than in 

 fig. 51, from a hyoglossus. 



3. The period of relaxation is at first markedly decreased. With 

 higher loads it tends to increase again, often to a considerable degree. 



4. The heights of the contraction progressively diminish as the 

 load rises. 



III. THE INFLUENCE OF VERATEINE 



Experiment 6. — Destroy a frog's brain by pithing, leaving the spinal 

 cord intact. Inject 5 minims of a 0*005 per cent, solution of veratrine dis- 

 solved in normal saline solution by the aid of a drop of weak sulphuric acid. 

 Arrange the apparatus for taking a single contraction, but with the drum to 

 rotate at a much slower rate (about 6 cm. per minute). After about half an 

 hour pith the spinal cord and dissect out the gastrocnemius and sciatic, and 

 fix the muscle in the myograph. In the preparation of the muscle care 

 should be taken to avoid stimulating it or its nerve. Adjust the writing 

 point to the blackened surface, and set the drum rotating. At any instant 

 the muscle may be stimidated by opening the break key by hand. Note that 

 the excitability is diminished, and a stronger stimulus than usual is required. 

 The contraction will be effected quickly, but the relaxation is carried out 

 very slowly, occupying some seconds. As soon as the muscle has completely 

 relaxed, stimulate it once more. It will be found that the character of the 

 twitch is completely altered. It is much more rapid. One or two more 

 contractions may also be recorded, and then the muscle allowed to rest for a 

 time. If it be then once more stimulated it will be found that the muscle 

 has again retmned to its previous state and the contraction is greatly pro- 

 longed. 



The most satisfactory preparation to use for this experiment is the 

 hyoglossus. This is attached to the lever in the usual way, and then a few 

 drops of a 1 per 100,000 solution of veratrine in normal saline is injected into 

 the large lymph sac in which the hyoglossus lies. If a very weak solution be 

 directly employed in this way the muscle is ready for use almost at once, 

 and the experiment never fails. 



Fig. 53 represents two curves produced in such an experiment. 

 Curve i is the first twitch, and curve n the sixth recorded. The first 

 curve shows the characteristic effect produced. The early part of the 

 period of contraction is effected as rapidly as in a normal twitch, but 

 the latter part is very slow, lasting three seconds. The period of relaxa- 

 tion is 46 seconds. In curve n the total duration of the twitch 

 has greatly diminished, viz. to 18 seconds, and another feature is 

 present which is highly characteristic of veratrine ; namely, that there 

 is a double apex. The first contraction is carried out almost as 

 rapidly as in a simple twitch, and it is then followed by a second con- 

 traction of very slow course, with rounded apex and showing a slow 

 relaxation. The form of such a curve varies considerably in different 

 instances. Sometimes the muscle may almost completely relax before 

 the second contraction sets in, or again the second contraction may 

 follow the first when that has reached its apex as in tracing i. If 



E 



