308 SPECIAL PHYSIOLOGY. 



uted to the modifying and diffusive influence of the ganglionic cells, 

 through which they are supposed to be transmitted. (Fick.) 



The influence of the van-motor nerves over the smaller arteries, is 

 shown by dividing the sympathetic nerves distributed to any part, as, 

 for example, in the neck of a rabbit, when the small arteries of the 

 corresponding side of the face, and of the ear, become dilated, the 

 blood collects in them, and accumulates, as is manifested by their 

 dark red appearance and increase of temperature, arid by the general 

 exaltation of the vital powers of all the tissues: the temperature is 

 sometimes elevated as much as 18 ; perspiration covers the skin ; the 

 venous blood is brighter, and coagulates more quickly than usual. 

 The retina becomes more sensible to light ; the pupil contracts, the 

 eyelids are partially closed, the membrana nictitans projects, the eye- 

 ball is retracted, and a flow of tears takes place. The muscles are 

 more irritable ; the rigor mortis appears more slowly, and lasts longer ; 

 inflammation and the reparation of injuries, effusion of serum, suppu- 

 ration, and absorption of extravasated blood, and the process of cica- 

 trization, occur more quickly, and are more active. If now the upper 

 portion of the cut sympathetic nerve be irritated by galvanism, the 

 vessels again contract to their usual size, the parts assume their 

 natural appearance and condition, and all the preceding phenomena 

 are exactly reversed. These singular effects are more marked, if the 

 cervical ganglia are destroyed. Other experiments likewise appear to 

 exhibit the power of the sympathetic over the circulation, tempera.ture, 

 and vital properties of the tissues. Thus, division of the roots of the 

 spinal nerves of the upper limb, before they leave the spinal canal, 

 causes loss of sensation and motion in the limb, but no change of tem- 

 perature ; whereas division of the large nerves of the limb, subsequently 

 performed, is at once followed by a rise of the temperature of the part, 

 certain fibres being then divided, which must have their origin directly 

 in the sympathetic ganglia, or else must pass through them, from 

 some distant part of the spinal cord. (Bernard.) So, also, increased 

 vascularity and temperature of the lower limb, but no loss of sensa- 

 tion or motion, have been found to follow destruction of the lumbar 

 sympathetic ganglia. But Schiff asserts, that the temperature of a 

 limb is elevated, after section of the anterior roots only of its spinal 

 nerves. 



This control of the sympathetic over the calibre of the small arte- 

 ries, is believed by some to explain its influence on the processes of 

 secretion and nutrition. The former have been already mentioned, in 

 speaking of the functions of the facial and fifth nerves ; but it may be 

 added, that the flow of tears from pain, and the partial sweatings of 

 one side of the face, after division of the sympathetic of the same 

 side, are further examples of this influence. The sympathetic vasi- 

 motor nerves appear to act, by causing contraction of the vessels, so 

 as to diminish their calibre ; and the dilatation which ensues on their 

 division or exhaustion, not only increases the supply of blood, but 

 also the permeability of the coats of the bloodvessels themselves. 

 Division of the sympathetic nerve in the neck is, after a time, fol- 

 lowed by opacity and ulceration of the cornea. The amaurosis, which 



