226 CENTRAL NERVOUS SYSTEM 



Nevertheless, the blood, arterial as well as venous, is bright 

 scarlet in color, owing to the little oxygen consumed by the 

 tissues. A hibernating dormouse has been observed to gain in 

 weight, which was due entirely to an excess of oxygen taken 

 in. Muscles and nerves remained irritable, and stimulation of 

 the vagus produces a still further slowing of the heart beat. 



Hypnotism. This state is analogous to, but by no means 

 identical with, sleep. It differs in a peculiar loss of voluntary 

 control over the muscular powers; in frequent anesthesia and 

 hyperesthesia ; in the great clearness of psychical images, which 

 may be forgotten, however, upon awakening, but are remem- 

 bered in subsequent trances. In the lighter stages the mind 

 sees clearly what is going on about it, which is not true in sleep. 

 Finally, hypnosis is characterized by an extraordinary obe- 

 dience to suggestions. The power of inhibition residing in the 

 cerebrum, by which the mind is constantly controlling and 

 arresting reflex movements, seems to be diminished if not 

 absent. Verworn has shown that the so-called hypnotism in 

 animals is not due to an inhibition from the cortex, since the 

 phenomena are obtained easily in decerebrate individuals. 



QUESTIONS ON CHAPTER XII 



How may the central nervous system be divided? 

 What is a neuron? 



How do the branches of nerve cells end? 

 What is the general function of the nervous system? 

 What are afferent, efferent, and central neurons? 

 What is a reflex act? 

 Describe the path of a simple reflex. 

 Discuss the phenomenon of inhibition. 

 Discuss the spread of impulses in the cord. 

 Name the afferent paths to the brain. 

 Name the efferent paths from the brain. 



Discuss in detail the paths of motor and cutaneous impulses. 

 Describe the effects of removal of the spinal cord. 

 What is meant by the tonic activity of the cord? 

 Discuss the knee-jerk, its variations and reenforrement. 

 What is the time value of an average reflex action? For what reasons 

 does it vary? 



Distinguish between reflex time and reaction time. 



Define personal equation. 



Discuss the medical significance of some reflexes. 



What is Babinski's sign? 



Describe briefly the functions of all the cranial nerves. 



Give the functions of the medulla oblongata. 



What is a centre? 



