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EXPERIMENTAL PHYSIOLOGY 



lasting some time after stimulation ceased. This is called a Pressor 

 effect. The only variations in the character of the tracing are due 

 to differences in respiration, which produce secondary effects upon the 

 blood pressure, fig. 138. Often, too, struggling movements are pro- 

 duced, especially if the animal be only lightly under the anaesthetic, 



Fig. 138. — Stimulation of the Central End of the divided Sciatic. The 

 Latter Portion of the Eespiratory Tracing is imperfectly recorded. 



when with each convulsion the blood pressure rises considerably. The 

 only completely satisfactory method of obtaining a pure pressor effect 

 is to previously curarise the animal. The reflex muscular movements 

 are then absent, and the pressor effect is produced unmasked by the 

 rise of pressure caused by each convulsion. The tracing of fig. 139 



