124 DR RUTHERFORD ON THE INFLUENCE OF THE YAGUS 



forming three peripheric motor centres connected with the vascular system, the 

 only ones as yet known. But it is interesting to observe that the submaxillary 

 and cardiac ganglia are obviously very directly connected with the medulla 

 oblongata by motor and inhibitory nerves, and although nothing can be stated 

 with precision regarding the central connections of the ganglia presiding over 

 the vessels of the penis, they have, nevertheless, probably an intimate con- 

 nection, like the others, with the medulla. The dilatation of vessels which 

 results from the action of these vaso-inhibitory nerves is, as regards the vessel, 

 passive ; it is due to the elasticity and blood-pressure being no longer opposed 

 by the action of the contractile elements of the vascular wall, these having been 

 brought to rest by a cessation of action in the vasomotor nerve apparatus. 



The vasomotor nerves may have their action increased as well as diminished 

 by the action of other nerves. The contraction of vessels in distant parts by 

 the sudden application of cold to it may be a small extent of skin. The remark- 

 able increase in the blood-pressure which follows stimulation of the central end 

 of the superior laryngeal nerve (Aubert and Soever),'" the contraction of 

 vessels and increase of blood-pressure which usually follows the gentle stimula- 

 tion of the central ends of mixed nerves, are some of the facts which support 

 this idea; such nerves may be very appropriately termed excito-vasomotor 

 nerves. These nerves appear all to pass inwards to the vasomotor centre in 

 the medulla oblongata. 



Other facts might be mentioned, but I may briefly say that every advance in 

 our knowledge of this question only tends more and more convincingly to show 

 that the innervation of the contractile elements of the blood-vessels is similar to 

 that of the cardiac muscular fibres. These contractile elements are directly 

 supplied by motor nerve fibres ; and the evolution of energy in the cells con- 

 nected with the latter may be diminished by one set of nerve fibres — cardio and 

 vaso-inhibitory — and increased by another — excito-cardio and excito-vaso- 

 motor. 



The idea commonly prevails that when a part becomes the seat of active 

 nutritive change, its blood-vessels undergo dilatation by reason of the increased 

 attraction for blood manifested by the tissues. The vis a f route, is supposed to 

 become so powerful that it can overcome the contraction of the arterial walls, 

 and thereby produce dilatation. It struck me that the vascular dilatation in 

 such a case is possibly the result of an influence transmitted by the tissue 

 through its vaso-inhibitory nerves. The only author who has come near to this 

 idea is Loven. A considerable time after the above had presented itself to my 

 mind, he published the excellent memoirt to which reference has already been 

 made. He showed that the blood-vessels of a part may be dilated by artificial 



* Centralblatt, 1868, p. 578. f Llh - cit - 



