CHAP. XXI.] FUNCTION OF THE SYMPATHETIC. 143 



to be correct, justify us in affirming that the sympathetic exhibits 

 marked indications if not of independence, yet of great peculiarity, 

 in its mode of distribution. Clinging to the coats of arteries, it 

 follows them for the most part in their ramifications, and attaches 

 itself to them somewhat as ivy does to a tree. Yet of the mode of 

 termination of the gelatinous fibres of the sympathetic, and of the 

 nature of their relations with the elements of the tissues among which 

 they lie, nothing certain is known ; a fact attributable in a great 

 degree to their want of such obviously distinctive characters as the 

 tubular fibres possess. These latter, after leaving the blood-vessels 

 are probably distributed either to sentient surfaces or to muscles 

 in the ordinary way. 



The proper mode, then, of stating the reply to this question seems 

 to us to be : that the sympathetic, taken as a whole, is not in itself 

 a special and independent nervous system, but a portion of the 

 nervous system peculiar in its composition, having, as regards some 

 of its constituent fibres, a special relation to blood-vessels, parti- 

 cularly arteries, (and these are the fibres which are independent of 

 the cerebro-spinal centres, having distinct centres of their own,) but 

 being by others of its fibres connected, as all other nerves are, with 

 the cerebro-spinal centres. 



II. The second question affects the endowments of the consti- 

 tuent fibres of the sympathetic. 



If we interrogate anatomy, we learn that the ramifications of this 

 nerve are distributed to muscles as well as to sentient surfaces. 

 The heart, for instance, derives its principal supply of nerves from 

 this source. The intestinal canal between the stomach and the lowest 

 part of the colon receives no nerves direct from the cerebro-spinal 

 system, and is therefore dependent solely on the sympathetic, for 

 whatever of sensibility it enjoys, or for such motor power as may 

 be usually called into action by nervous influence. We, therefore, 

 must infer from anatomy that the sympathetic contains both sensi- 

 tive and motor fibres. 



Many experiments lead to a similar conclusion. Stimulation of 

 the cervical ganglia excites the heart to increased action ; and irri- 

 tation of the splanchnic nerves causes increased vermicular motion 

 in the stomach and intestinal canal. Miiller proved a similar result 

 to ensue upon irritation of the cseliac ganglion. He exposed the 

 intestines, and likewise the cseliac ganglion in a rabbit; he waited 

 until the increase of peristaltic action, which exposure to the air 

 always produces, had subsided, and then he applied potassa fusa to 

 the ganglion, when immediately the peristaltic movements became 



