i68 THE MECHANISM OF THE CIRCULATION. 



powers as follows : 1. Nerves which always produce a fall of arterial tension 

 (e.g. the depressor). 2. Nerves which sometimes produce a fall, sometimes a 

 rise (e.g. the vagus). 3. Nerves which usually occasion a fall (e.g. the glosso- 

 pharyngeal). 4. Nerves from which primary depressor effects can only be 

 obtained by special means (e.g. the sciatic, anterior crural, ulnar, median, and 

 intercostal). 



He states that the power of the depressor nerve, which acts mainly on the 

 splanchnic area, is not abolished by curari. On the other hand, the depressor 

 power of other afferent nerves, which act mainly on the vascular areas of the 

 skin and muscles, is abolished by curari. 1 



1 It has been stated on p. 146 that Gulland has failed to demonstrate vasomotor nerves 

 in the vessels of the pia mater. Since then, however, various observers, including Gulland 

 himself, have been able to show the usual peri vascular nerve-plexuses upon the cerebral 

 vessels, Brit. Med. Journ., London, 1898, vol. ii. p. 781. The existence of cerebral vaso- 

 motor nerves cannot therefore be denied, and we must assume that the experimental 

 evidence remains as yet inconclusive, owing to the extreme difficulty of separating passive 

 changes, brought about by the slightest alterations in the general circulation, from active 

 vasomotor effects. Note added in September 1898. 



