120 H. E. HIMWICH VOL. 4 (1950) 



pressure. This stage is not unlike that of sham rage exhibited by the decorticate animal. 

 The third constellation (area 3) represents functions allocated to the midbrain. For 

 example the body is seized by violent (tonic) spasms during which the legs become ligidly 

 extended, the trunk is arched while the arms are thrust forward, bent at the elbows. 

 The fourth group of manifestations, referable to the pons and upper portion of the 

 medulla (area 4), begins when the arms are no longer held in front of the body but are 

 slowly forced back over the head (extensor spasm). The back however is arched the legs 

 are extended as in the third stage and the entire picture is similar to that of a decerebrate 

 animal. Finally in the fifth stage (area 5) the cold, gray, clammy skin, the slow and 

 feeble heart, the greatly depressed respiration, the muscular flaccidity, and the con- 

 tracted pupils all give evidence that the metabolic depression is now affecting the vital 

 medullary centers. 



Soon after the fifth group of signs appear it is necessary to give the patient sugar. 

 The blood glucose values rapidly rise and the brain once more obtains adequate supplies. 

 The alterations in behaviour during recovery conform to the same plan as those seen 

 during their development but this time their order is reversed. 



It is well to make comparisons with the results of metabolic depression other than 

 those produced by hypoglycemia. If the signs are due to a metabolic deficit then the 

 same or at least a similar series of signs should be produced irrespective of the manner 

 by which the metabolic deficit is created. As an example let us consider anoxia, a con- 

 dition in which oxygen is no longer available to the brain in common with the other 

 organs. 



It is true that energy may be provided in the absence of oxygen, an anaerobic 

 mechanism of great biological importance, for example, in sudden muscular activity. 

 In the brain however, though not without significance^^' ^^' 2^, the anaerobic release of 

 energy is strictly limited for most of the energy usually available in the carbohydrate 

 foodstuff of the brain, glucose, cannot be realized. For that reason the brain is highly 

 sensitive to oxygen lack and when thus bereft of energy, can no longer support its own 

 functions. 



Whereas the signs of hypoglycemia may be observed over a period of 5 hours 

 those of acute anoxia are more fleeting and must be limited to a period of as many 

 minutes. Nevertheless the changes in behaviour follow the same general path of those 

 of hjrpoglycemia and indicate a downward progression during anoxia and the reversed 

 direction on recovery. These signs were demonstrated in a series of psychotic patients 

 who respired undiluted nitrogen administered by means of a mask^^. Early is seen a 

 brief period during which consciousness becomes impaired as the cerebral hemispheres 

 are the first to suffer from the decrease in available energy (area 1, Fig. i). The first 

 phase ends as environmental contact is lost. With the loss of consciousness a series of 

 dramatic neuromuscular reactions occurs beginning with a period of aimless motor 

 restlessness which ensues after the subcorticodiencephalon acquires freedom from cor- 

 tical restraint (area 2). Next come strong muscular contractions like those described in 

 the third phase of hypoglycemic coma (tonic spasms) as the midbrain is freed from higher 

 control (area 3). Finally emprosthotonos, flexion of the body, or opisthotonos, extreme 

 extension, are seen in the fourth stage (area 4). These signs are release phenomena and 

 indicate a decerebration of functional origin. At this point the inhalation of nitrogen 

 is stopped to prevent involvement of the medullary centers. With the subsequent ad- 

 ministration of air or oxygen the normal cerebral integrations are rapidly restored. 

 References p. 125. 



