Changes in Reflex Thresholds. 



59 



144 (1322) 



Changes in reflex thresholds following experimental shock from 

 intestinal manipulation. 



By Eugene L. Porter (by invitation). 



[From the Physiological Laboratory of the University of Pennsyl- 

 vania.] 



Insensibility and apathy are common clinical observations in 

 traumatic or surgical shock. Meltzer and others have reported 

 similar observations when the shock is produced experimentally 

 by withdrawing the intestines from the abdominal cavity and 

 cooling or manipulating them. I have repeated this procedure 

 with spinal cats and have subjected to quantitative measurement 

 the effects produced on the cord. The cats are made spinal by 

 pithing the brain through the foramen magnum. The flexion 

 reflex is elicited by stimulation of the posterior tibial nerve and 

 recorded by contractions of the tibialis anticus muscle. The 

 Martin system of measuring the break shocks to the nerve is used. 

 In such a preparation, left to itself at normal temperature, the 

 threshold of the flexion reflex remains very constant for long 

 periods of time, changing, if at all, very gradually. Ordinarily 

 the changes between successive readings are fractions of a single 

 unit of measurement. If, now, the intestines be withdrawn from 

 the abdominal cavity and manipulated, in about 50 per cent, of 

 the animals operated on, this threshold rises very promptly — 

 within two or three minutes ordinarily — and within ten minutes 

 it may have reached a value 50 per cent, greater than before 

 manipulation. It commonly remains at this high level during 

 manipulation. Upon cessation of the manipulation the threshold 

 drops, and within ten minutes or less, it may be at its original 

 level and continue at this level, showing as slight variations as 

 before the manipulation. In such cases it may be possible to 

 repeat the procedure on the same animal. 



To take a specific case: 



Experiment of July 10, 1917. 

 3.13 Threshold 15.5 Z units. 

 4.36 Threshold 14.3 Z units. 



