EXHAUSTION IRRITABILITY. 229 



strength) hence the spine is bent. If this condition 

 tends to pass on into sleep, this is expressed by 

 the preponderance of the orbicular muscle over the 

 levator of the upper lid, and the other signs of .sleep 

 supervene. 



Exhaustion is an extreme condition of fatigue, 

 in which movement (the kinetic function) is alto- 

 gether lowered. The face becomes toneless, and 

 devoid of fine mobile expression; the orbicularis 

 palpebrarum is relaxed; the face may be length- 

 ened from relaxation of its muscles ; the ordinary 

 movements of expression are not excited by the 

 ordinary stimuli, and such movements as do occur 

 are slow and laboured. A strong stimulus is re- 

 quired to induce the man to hold out his hands, 

 and then the posture is " the feeble hand." Sighing 

 .and yawning are common; speech is slow, and 

 the tone of the voice is altered ; in some cases 

 finger-twitching, especially of separate fingers, in- 

 dicates extreme exhaustion and irritability. 



Irritability is expressed in a man when a slight 

 noise makes him start. This is a reflex movement in 

 excess, a reflex action that does not occur in perfect 

 health on so slight a stimulus. In irritability other 

 stimuli besides sound may produce excessive reflex 

 action. A touch upon the shoulder causes a sudden 

 movement. Not only is the amount of reflex move- 

 ment excessive, and out of proportion to the 

 stimulus, but the kind of movement, or special 

 series of movements, may -differ from that usually 

 following from the stimulus in health. A child 

 three years of age, when irritable, may turn away 



