6 CORA SENNER WINKIN 



with extra-pulmonic pressure through the operative procedure, artificial 

 respiration could be dispensed with as long as the medullary cells 

 remained functional. 



Prior to occlusion, ether was reduced until various obvious tests 

 of the activity of the brain stem could be secured, the return of a vigorous 

 corneal reflex always being awaited before the circulatory arrest was 

 made. With the elicitation of the corneal reflex, artificial respiration 

 was begun, and the clamps on the arteries immediately adjusted. Care 

 is needed to include all the arterial branches isolated in the clamps. 



With the adjustment of the clamps, the entire series of peripheral 

 effects follows; the eye reflexes are immediately lost, and within about 

 20 seconds the more marked peripheral effects are released. Deep and 

 labored breathing sets in, skeletal convulsions appear, and a sharp rise 

 of blood pressure is recorded which often reaches 200 mm. Hg. or more 

 (fig. 5a). This frequently outlasts the other functions; the pressure 

 may not begin to fall until some 10 to 80 seconds after respiratory 

 failure. 



The time from the shutting off of the arteries to the circulatory 

 failure is then taken as the complete occlusion time. On the average, 

 this occupied 3 minutes. 



Immediately following reestablishment of the circulation there is a 

 profound depression of all functions. Blood pressure continues falling 

 markedly when the arteries are released, and finally reaches a level of 

 about 50 mm. No other medullary responses are elicitable at this time. 

 Artificial respiration is, of course, maintained throughout the period of 

 depression, and until such time as the bulbar functions again become 

 evident. 



If no further lesions are inflicted, occlusions of 3 to 4 minutes are 

 usually followed by a beginning of recovery within 5 to 7 minutes after 

 release of the arteries. Blood pressure usually starts rising first, and 

 after a rise of 10 to 15 mm. spontaneous respiratory gasps reappear. 

 Pressure continues to rise, respiratory movements become more and 

 more frequent; soon normal pressure is regained and the animal breathes 

 quietly and regularly. Ten to 15 minutes after release of the arteries, 

 pressure is usually normal, vibrissae are erect, and the corneal reflex 

 is again elicitable. At this point, a renewed occlusion of the head 

 arteries may be done and the entire cycle repeated. 



The modification of anatomical conditions was usually carried out 

 in the interval of depression following a control occlusion. In this 

 way further etherization was avoided. Except under certain specified 



