STUDY OF THE CIRCULATION IN MAMMALS 



that side will be warmer and redder, (a) Stimulate the upper end of 

 the sympathetic : the pupil dilates, the third eyelid is retracted, some 



of the hairs on the side of 

 the head may be erected, 

 and the arteries of the ear 

 contract, so that the whole ear be- 

 comes pale, (b) Stimulate the upper 

 end of the depressor whilst the blood- 

 pressure is being recorded. After a 

 long period of latency there is a fall 

 of pressure which lasts during stimu- 

 lation of the nerve and for a short 

 time after its cessation. 



7. Inject into the jugular vein 

 a few drops of an extract of the 

 suprarenal capsule of any animal or 

 a very small dose of adrenalin. The 

 extract is made by taking 20 c.c. of 

 Ringer's solution to each gramme of 

 suprarenal capsule, boiling and filter- 

 ing. Record the effect 

 on blood - pressure. 

 Notice the dilatation 

 of the pupils, the re- 

 traction of the third 

 eyelid, and the pallor 

 of the ears. If a 

 plethysmograph is be- 

 ing used, the record 

 of the effect on the 

 contained organ usu- 

 ally indicates con- 

 traction of arteries. 

 The experiment can 

 be repeated more 

 than once. 



FIG. 74. Diagram of method of recording the blood- 

 pressure in the pulmonary system, a, 6, c, as in 

 Fig. 73 ; d, bottle of bicarbonate solution with 

 loosely fitted cork ; e, manometer tube with scale 

 in centimetres and millimetres ; /, piston-recorder ; 

 g, writing point. 



