THE HYOGLOSSUS PREPARATION 2L 



cisions down to the shoulder girdle. The lower jaw is then pulled 

 slightly forwards, and by a single transverse incision at the upper edge 

 of the shoulder girdle the whole of it is removed. It is now placed 

 mucous surface upwards, the tip of the tongue lifted up and either 

 transfixed with a hook, or a fine thread is tied round it. The tongue 

 is then turned forwards and extended out of the mouth. The body 

 of the hyoid cartilage now stands out clearly, and this may be 

 transfixed by a pin, and in that way fixed to the cork of a myograph, 

 or the cartilage may be directly clamped in a muscle forceps. The 

 thread or hook may then be attached to the writing lever. The great 

 advantage of the preparation is that the muscles are composed of long 

 fibres strictly parallel to one another, which are completely protected 

 from any injury during the preparation, because the muscle itself is 

 not exposed. Remaining in situ the whole time, they are protected 

 from drying by the mucous membrane of the tongue and mouth, and 

 on the ventral side by the skin of the jaw. 



If we wish to stimulate indirectly, the two hypoglossal nerves 

 can be easily isolated and laid upon electrodes. The only disadvantage 

 lies in the small size of the muscle, but the many advantages which it 

 possesses give, in the greater number of experiments, full compensation 

 for that. disadvantage. 



THE GRAPHIC METHOD 



Most of the movements carried out by the different parts of the 

 body, and which it is our object to study, are performed at so rapid a 

 rate that the unaided eye is only able to give us a judgment of the 

 broad outlines of the movement. By it alone we are quite unable to 

 gain any accurate knowledge of the details of a particular movement. 

 For instance, if we expose the heart of a recently killed frog, and 

 watch it beating, it is difficult to be certain that the auricular beat 

 precedes the ventricular, and in many cases it is quite impossible to 

 determine with any certainty whether the contraction be carried out 

 at a faster or slower rate than the dilatation, or, if there be a difference, 

 to determine the amount of that difference. Still more is the difficulty 

 perceived if we turn our attention to a more rapid movement, such as 

 a single twitch of a frog's muscle, where the whole cycle of movement 

 is so rapid that we are quite unable to accurately judge of its amount, 

 or of any variation in the rate of its contraction or relaxation. We 

 require, then, some means of obtaining a permanent record of each 

 movement which we may afterwards study at our leisure ; and this 

 means is afforded us by what is termed the graphic method, the 

 general principle of which is that the part in movement is made to 

 record its movement by writing it upon a surface. Thus ii we wish 



