364 PHYSIOLOGY CHAP. 



function it was no longer possible to obtain reflex vaso- 

 constriction on exciting the sciatic, the opinion generally held was 

 that the cord contained no other centre capable of influencing the ' 

 tone of the vessels independent of that in the spinal bulb, and 

 that this was probably the only true vasomotor centre. Very 

 soon, however, other experimental observations came to light 

 which showed the fallacy of this view, and led to the opinion that 

 there were secondary vaso- cons trie tor centres along almost the 

 whole of the cord, which were able to function after the principal 

 bulbar centre had been cut out. 



Goltz was the first to propose this theory (1864-74). He 

 found in the frog that the vascular atony was far from complete 

 after extirpation of the entire brain, including the bulb, and 

 became so only after destruction of the spinal cord. He further 

 observed iu dogs that when the cervico-dorsal tract was cut off by 

 division from the lumbo-sacral, and the animal kept alive until 

 the vascular atonia of the hind - limbs had disappeared, this 

 atonia was reproduced on destroying the lumbar cord. He 

 concluded that the restoration of vascular tone after section of the 

 cord was due to the presence of vasomotor centres in the lumbar 

 medulla. 



When cut off from the bulb, the spinal vasomotor centres are 

 also capable of reflexly constricting the vessels, and of raising 

 arterial pressure, when excited, as was first shown by Schlesinger 

 (1874) in dogs and rabbits, after he had increased the excitability 

 of the cord by injecting minute doses of strychnine. This fact 

 was subsequently confirmed by many observers. 



In curarised animals, when the cord is separated from the 

 spinal bulb, the asphyxia produced by cessation of artificial 

 respiration suffices to cause vascular constriction, as was first 

 demonstrated by Kowalewsky and Adamiik (1868). Since this 

 effect depends on excitation of the spinal centres, it follows that, 

 after destruction of the cord, asphyxia no longer exercises any 

 pressor action (Schlesinger, Luchsinger, Konow, and Stenbeck). 



The spinal centres for the vaso-constrictors lie not only in the 

 lurnbo-sacral region (Goltz), but also in the dorsal tract (Vulpian 

 and Kabierscki). On the other hand, they appear not to exist, or 

 to be very scanty, in the cervical tract, since aortic pressure is not 

 affected by section of the cervical cord at any height, after the 

 bulbar centre has been cut off (Strieker). 



The vaso-constrictors in the bundles of the cord for the most 

 part run directly, and only follow the crossed paths to a minor 

 extent (Brown-Se'quard and Schiff), as appears from the effects of 

 hemisection of the cord. They are chiefly mingled with the 

 sensory and motor fibres to the skeletal muscles which make up 

 the lateral bundles (Dittmar), as shown by the effects of partial 

 section in different segments of the cord. 



