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Scientific Proceedings (107). 



respiration. In many cases the experiments were continued 

 until there was a failure of respiration which was likely to occur 

 when the pressure had risen to from 250 to 300 millimeters of 

 saline. In other cases they were intermitted when respiration 

 was observed to be labored. The curve always had much the 

 same form indicating a slow rise in pressure in proportion to the 

 volume up to a critical point, after which the pressure increased 

 much more rapidly, as though such a point indicated the end of 

 the ability of the musculature to lengthen with a minimum 

 increase in pressure and thereafter exhibited only elasticity. 



The anesthesia, when neither very light nor very deep, had no 

 effect upon the pressure, volume remaining constant. Very 

 light anesthesia sent the pressure up, and very deep anesthesia 

 sent it down a little. Decerebration had no effect upon it. 



The next step was to determine whether ablation of the motor 

 nerves of the abdominal musculature would have any effect upon 

 the pressure curve. After the control curve had been taken, 

 therefore, the fluid was removed from the abdominal cavity and 

 no further procedures were undertaken for an hour. The three 

 branches of each phrenic nerve were then removed and the filling 

 of the abdominal cavity was repeated. 



In a similar manner, after obtaining the normal curve in other 

 cats, the ventral roots of the spinal nerves from the mid-thoracic 

 through the lumbar region were destroyed (laminectomy having 

 previously been done) and another curve obtained. 



Removal of the phrenics with paralysis of the diaphragm 

 was in all cases found to cause a slight increase in pressure 

 proportionate to volume, and the same was the case with removal 

 of the spinal nerves. The curves, however, were so closely parallel 

 to the normal curve as to be hardly significant. In order to obtain 

 the effect of isolation of the muscle from all motor impulses, 

 curare was injected into the femoral vein of a number of cats and 

 artificial respiration was maintained. There was little variation 

 from the control curve. 



After the death of the animal, curves were taken of the pressure 

 at intervals of one and three or two and four hours in order to 

 determine the role played by the intrinsic elasticity of the mus- 

 culature in the maintenance of this curve. With each succeeding 



