224 THE DUCTLESS GLANDS 



cut across high up, and artificial respiration carried out. The 

 blood-pressure was recorded from the carotid or the femoral 

 artery. Stimulation of the splanchnic nerves gave rise to a 

 marked rise of blood-pressure, and continuous stimulation 

 produced a long -continued elevation of pressure. The rise did 

 not occur if the adrenal veins were tied. 



Tscheboksaroff has reached the same conclusions as Dreyer 

 did viz., that the great splanchnic nerve in dogs is the true 

 secretory nerve of the adrenal body, and that its stimulation 

 leads to an increase of the adrenin which is found in the venous 

 blood. Section or ligature of this nerve diminishes the amount 

 of adrenin in the blood. 



The theory that the chromaphil tissues (and especially the 

 medulla of the adrenal bodies) maintain, or help to maintain, 

 the normal tone of the bloodvessels and other sympathetically 

 innervated structures, has been already discussed. Evidence 

 has also been given that the medulla of the adrenal body is 

 not essential to life, and that the reduction of the adrenin 

 content of the blood to a minute fraction of the normal amount 

 does not affect the health of an animal. 



These statements, however, do not exclude the possibility 

 that the chromaphil tissues play a part in certain reactions 

 which are initiated elsewhere, as, for example, in those which 

 result from stimulations of nerves in laboratory experiments. 



We have referred above to certain experiments involving 

 stimulation of the splanchnic nerve, and its effect on the blood- 

 pressure. This question must now be treated in greater detail. 



It has been known for a long time that the rise of blood - 

 pressure brought about by stimulation of the peripheral end 

 of the splanchnic nerve is not simple. The curve obtained sug- 

 gests at once that there is more than one factor concerned in 

 its production. 



Johansson found that in the dog the curve presents two 

 summits, and it has since been found that the same is generally 

 true in other animals also. 



Lehndorff also worked with dogs and came to the conclusion 

 that the first rise is due to vasoconstriction in the splanchnic 

 area, the " step " to a temporary dilation of the heart, and the 

 second rise to increased force and frequency of the heart-beat 

 accompanied by vasoconstriction in the somatic area. 



Elliott, who investigated the subject in cats, stated that in 



