GRAPHIC OP ARTERIAL PRESSURE 41 



tlie arterial pressure in the decapitate pre- was analysed by T. Lewis and G. C. Mathison 



paration see Sherrington, Jnl. of Fhysiol. {Heart, vol. ii, p. 47 ; 1910). 



xxxviii, 375, 1909. The onset of the The main factor in the production of 



asphyxial rise of pressure is much slower this asphyxial a. p. curve is lack of oxygen ; 



in the decapitate preparation than where precisely similar curves are produced by 



the bulbar vasomotor centre remains ; in ventilating the lungs with nitrogen. For 



the latter case the rise begins in about discussion of the COj, or acidosis, factor see 



5"-20'^ as against 80"- 160" or more in the G. C. Mathison, 1910, Jnl. of Physiol 



former. The sudden change in pulse-rate vol. xli, pp. 416-49 ; Heart, ii. 54 ; also 



due to heart-block (Sherrington, I. c. ; Roaf Starling's Princijiles of Human Physiol., 



and Sherrington, Q. Jnl. Exp. Phys. iii. 209) p. 1112. 



EXERCISE YII 



AKTERIAL PRESSUEE, SPLANCHNIC NERVE AND ADRENAL GLAND; 

 PITUITARY EXTRACT; VASOCONSTRICTION IN KIDNEY AND GUT; 

 CHROMAFFINE REACTION; CHYLE; PULMONARY CIRCULATION-TIME. 



[Sections in brackets may be omitted at first performance of the exercise.] 



I. See that the decapitate preparation provided for you is being properly 

 ventilated and in good condition. 



II. Get ready apparatus : recording arterial manometer, induction 

 circuits and hand-electrodes, for stimulating splanchnic nerve, and needle- 

 syringe. Have at hand (a) pituitary extract, (/S) potassium bichromate, 2 per 

 cent, solution, (7) methylene-blue -2 per cent, dissolved in normal saline. 



III. Prepare the right carotid for kymographic observations as in 

 previous exercises, but leave the control thread and cannula thread loose, 

 to be used later when the cannula is inserted and connexion made with the 

 manometer. Close the wound with a clip. 



Exposure and Stimulation of the Splanchnic Nerve (PI. Ill, and text-figs. 20, 

 21, 22). 



IV. Operation. Lay the preparation on its left side, with the right hind- 

 limb extended by a weighted clip attached to one of the digits. Clip the hair 

 off the right loin, and make a straight incision (PI. Ill, fig. 1), about 7 cm. long, 

 parallel with and about 5 cm. to the right of the dorsal mid-line. This 

 incision should pass over about the middle of the last rib. The headward end 

 of the incision should lie as far forward as the eleventh rib ; thirteen is the 

 normal number of ribs in the cat. The posterior end of the incision will lie 

 about half-way between the crest of the ilium and the last rib. Across 

 each end of the longitudinal incision make a transverse one extending about 

 2 cm. to either side of it. Keflect the skin and clip back the skin-flaps. 



