QUESTIONS AND ANSWERS 131 



production of heat by the oxidation of the carbohydrates, glycogen 

 and sugar. 



Define muscular excitability. What conditions tend to (a) impair 

 muscular excitability, (b) enhance muscular excitability? 

 Muscular excitability is the power possessed by muscles to 

 respond to stimuli. This excitability is independent of the motor 

 nerve, as may be shown by injecting curare into the muscle, when 

 stimulation of the motor nerve will not produce muscular contrac- 

 tion, but if the same stimulus is appUed directly to the muscle, con- 

 traction follows. 



(a) Fatigue and lessened blood supply. 



(b) By training and "conditioning" the voluntary muscles are 

 educated to work in the best and most economical manner; their 

 response increases in rapidity and power and their relaxation is 

 quickened to prevent loss of time. 



What changes take place in a muscle as a result of rigor mortis? 



The muscle becomes firm and solid, loses its elasticity and does 

 not respond to electrical stimuli. Its reaction is no longer alkaline, 

 but becomes acid owing to the sarcolactic acid formed. The proteids 

 coagulate, carbon dioxide is produced and heat is evolved. 



Nervous System 



Describe (a) an efferent nerve, (b) an afferent nerve. Give the func- 

 tion of each. 



(a) One conveying impulses from a centre to the periphery. 

 This impulse may cause contractions and movements of muscles, 

 blood-vessels and viscera, or, it may be inhibitory in character and 

 thus slow the heart, retard peristaltic action, etc. 



(b) One conveying impulses from the periphery to a centre. 

 The impulse may be one of the special senses, sight, hearing, smell, 

 etc., one of pain, heat, cold, etc. 



Classify nerves according to function and state the function of each 

 class named. 

 1. ' Afferent or sensory. 

 2. Efferent or motor. 

 See answer to preceding question. 



Describe the functions of the spinal cord. 



1. Conducts impulses from the periphery to the brain and vice 

 versa. 



2. Seat of numerous reflex actions. 



3. Takes some part in coordination. 



