12 PRACTICAL PHYSIOLOGY 



Identify the structures seen, and then make the observed person 

 sound a high note, a low note, and take a deep inspiration. 



NOTE. Before inserting the mirror in the mouth of another 

 individual it must be disinfected by plunging for one minute in the 

 lysol provided and then rinsing in water. 



(Read Physiology of Voice in Text Book.) 



PROPRIOCEPTIVE MECHANISMS 



I. The Power of Determining the Position and Movements of the 



Various Parts of our Bodies 



MUSCLE-JOINT SENSE 



METHODS. With the eyes closed, (a) put the various parts of 

 the arm, hand and fingers in any position, and try if the position 

 of each part can be determined by putting the opposite arm in the 

 same position ; (6) get some one to put the same parts in any 

 position, and again try if the positions can be accurately reproduced 

 on the opposite side. 



(c) Take some object in the hand and study how an estimate of its 

 weight is arrived at. Has the condition of the muscles, tendons, and 

 joints anything to do with it, and if so, what ? 



To test the delicacy of this sense find the smallest difference of 

 weight which can be detected, as in Appreciation of Pressure, 

 (p. 6, I. 2), but keeping the hand free of the table and using the 

 muscles of the arm. 



(d) By passing the hand over some object with the eyes shut, 

 study how this sense, in conjunction with touch, gives information 

 as to the distance, shape and size of external objects. 



II. The Power of Determining the Movements of the Head in Space 



LABYRINTHINE MECHANISM 



Study a model of the internal ear with special reference to the 

 arrangements of the semicircular canals. Under the microscope 

 study a cross section (1) through an ampulla and (2) through a 

 canal. 



Consider the absence of sensation of movement in a smooth- 

 running train, and the sensation of movement on starting and 

 stopping. 



1 . Spin rapidly round several times, stop and observe the sensation 

 produced. 



2. Hold a short stick or poker vertically with its point on the 

 ground. Place the forehead on the top and rapidly walk three 

 times round it. Then raising yourself straight, try to walk to the 

 door. Notice the effect produced and try to explain it. 



Try to come to a conclusion as to how the canals may act in the 

 above experiments. 



