UPON THE VASCULAR SYSTEM. 123 



lished that the contractile elements of the blood-vessels are supplied by motor 

 nerve filaments derived from the sympathetic. Diminution in the calibre of the 

 blood-vessels is produced by these nerves. According to Ludwig and Thiry, 

 the general centre for the vasomotor nerves is situated in the medulla oblongata. 

 This cerebro-spinal centre is more or less constantly in action, whereby vessels 

 are usually kept in a semi-contracted state. The amount of contraction in the 

 vessels — in other words, the degree of activity of the cells in the vasomotor centre 

 — may be increased or diminished by certain nerves which convey influences to 

 the medulla. Bernard""" was the first to show, by experiment, that vessels may 

 be dilated by the irritation of certain nerves. He found that when he divided 

 the auricular nerves in rabbits, and excited their central ends, the vessels of the 

 ear of the same side became turgid. Slight contraction preceded the dilatation. 

 LovENt has confirmed Bernard's observation, and has shown that dilatation of 

 vessels in the rabbit's leg follows irritation of its afferent nerves ; in short, that 

 dilatation of the vessels of a part may be produced by influences transmitted 

 through the afferent nerves of that part to the cerebro-spinal vasomotor centre. 

 Like Bernard, he found that transient contraction generally precedes the dila- 

 tation of the vessels so induced. The most remarkable instance of a nerve 

 capable of dilating vessels is to be found in the superior cardiac branch of the 

 vagus already alluded to. When this nerve is divided and its cranial end 

 stimulated, dilatation of abdominal blood-vessels takes place without any previous 

 contraction, such as commonly results when a mixed nerve such as the sciatic 

 or the trunk of the vagus is stimulated. In all the above cases the vascular 

 dilatation succeeds stimulation of the central ends of the divided nerves ; that is 

 to say, the peripheral end of the cranial portion of the divided nerve. Two 

 facts, however, have been discovered which are opposed to the idea that the 

 motor centre for all the blood-vessels of the body lies in the medulla oblongata ; 

 one concerns the submaxillary ganglion, the other, the ganglia upon the nervi 

 erigentes of the penis. It is well known that if the chorda tympani nerve be 

 divided, and its peripheral end stimulated, dilatation of the blood-vessels in the 

 submaxillary gland is the result. In like manner, as recently shown by 

 Eckhard| and Loven§, when the nervi erigentes are divided in the dog and the 

 peripheral portions stimulated, erection of the penis results, principally from the 

 dilatation of vessels induced by the irritation. On these nerves there are many 

 ganglionic corpuscles ; and the most feasible explanation of this vascular dilata- 

 tion in the case of the submaxillary gland and penis is, that the ganglionic cells 

 existing in connection with these structures, are in part, at any rate, vasomotor 

 cells, and correspond to the ganglia in the heart, These three groups of ganglia 



* Jl. cle la Physiologie, 1862, p. 416. \ Beitrage. Giessen, 1863. 



+ Lov£n, Ludwig's Arbciten, 1866, p. 1. § Lib. tit. p. 18. 



VOL. XXVI. PART I. 2 K 



