MECHANISM 271 



heap up pressure in some ampulla. Some work on fishes by 

 Maxwell and others gives an indication that this co-operation is 

 extremely probable. 



The alterations in extensor tone produced by stinnilatino of the 

 hair-cells of the vestibular apparatus are augmented by stimuli 

 coming from the muscles themselves, especially from those of the 

 neck, and by auditory and visual stimulation. The following 

 sentences taken from " Recent Advances in Physiology " may 

 make this clear. '' Suppose that a cat hears a mouse moving on 

 its right. The head is turned to the right ; this alters the centre 

 of gravity, but as a result of the tonic neck reflex, there is an 

 increase of tonus in the muscles on the right side of the body, 

 which preserves the balance by throwing the weight on the right 

 limbs. Now, because the left limbs are less loaded, they will ])e 

 the first to move if the animal springs to its prey, so that the cat 

 will automatically move in the right direction." Compare with 

 this statement the description given in Chap. XXXIII. of Ham- 

 mond's heliotropic dog. 



Further Reading 



Hartridge. In Starling's " Principles of Physiology." J. & A. Churchill. 

 LovATT Evans. " Recent Advances in Physiology." J. & A. Churchill. 



