SECRETION. 



467 



of sudden and violent passion. There can 

 be no doubt, however, that a disordered state 

 of the biliary secretion is frequently rather 

 the cause than the consequence of a melan- 

 cholic state of mind ; the blood being suffi- 

 ciently vitiated by a deficient elimination of 

 bile, to have its due relations with the nervous 

 system seriously disturbed, before any ob- 

 vious indications of that deficiency make their 

 appearance in the jaundiced aspect of the 

 cutaneous surface. 



These and similar phenomena afford clear 

 proof of the influence exerted over the 

 secreting processes by mental states ; and it 

 is scarcely to be imagined that this influence 

 can be exerted through any other channel 

 than the nervous system. If we further in- 

 quire to which division of the nervous system 

 we are to attribute the conveyance of this 

 influence, we shall find reason to regard it as 

 chiefly, if not entirely, operating through the 

 portion commonly known as the sympathetic. 

 For there are many secreting organs which 

 are supplied with no other nerves than those 

 which they receive from this division, so that 

 they cannot possess any connection with the 

 cerebro-spinal centres except through its 

 medium. The mammary glands, which are 

 supplied by the spinal nerves as well as by 

 the sympathetic, may be considered as re- 

 quiring such a direct communication with the 

 cerebro-spinal centres, inasmuch as their se- 

 cretion is made, for obvious purposes, greatly 

 dependent upon sensations directly affecting 

 themselves, which is rarely the case elsewhere. 

 The lachrymal and salivary glands would seem 

 to have a more direct and exclusive con- 

 nection than most others, with the cerebro- 

 spinal centres ; but perhaps this may be more 

 apparent than real, for the fifth pair, from 

 which they are supplied, seems in many re- 

 spects to combine the attributes of a sympa- 

 thetic with that of a proper cranial nerve ; 

 and bearing in mind the minuteness and the 

 universality of the distribution of the sympa- 

 thetic plexuses upon the trunks of the blood- 

 vessels, we see that even these glands, like 

 others, may be subjected to its influence. 



If we further examine into the mode in 

 which that influence is exerted, we shall, per- 

 haps, find reason to attribute it to the effect 

 of nervous agency, rather upon the walls of 

 the blood-vessels and upon their contents, 

 than upon the secreting structures themselves. 

 For, as already remarked, the variations in 

 the quantity of a secretion may be accounted 

 for by such an increase or diminution in the 

 access of blood as we know to take place, 

 through an alteration in the calibre of the 

 vessels, in the act of blushing or the paleness 

 of fright ; and the feelings experienced by the 

 nursing female harmonise well with this sup- 

 position. On the other hand, the perversion 

 of the quality of a secretion, which may take 

 place as a result of mental emotion, would 

 seem rather due to an alteration in the con- 

 stituents of the blood previously to the elimi- 

 nation of the secretion, than to the exercise 

 of any influence upon the secreting structure 



itself. For we find, in the case of the pecu- 

 liar odorous matter for example, that it may 

 be eliminated in a vaporous form by the air- 

 passages, or by the intestinal canal ; or that 

 its taint may be imparted to the liquid secre- 

 tions of the intestinal glandulae ; or, again, 

 that it may be communicated to the urinary 

 excretion : and this variety in the channels 

 of escape of the same kind of material, pretty 

 clearly indicates that it must have pre-existed 

 in the blood. There are many other facts 

 which confirm this view, by indicating that 

 the condition of the blood whilst circulating 

 in the vessels may be influenced by mental 

 emotions, which probably act upon it through 

 the medium of the sympathetic nerve ; but 

 of these it is scarcely the place to speak. 



Another class of evidence, as to the ex- 

 ertion of an influence by the nervous system 

 upon the secretory function, is furnished by 

 observation of the results of the interruption 

 of that influence, either by a diseased con- 

 dition of the nervous centres or nerve trunks, 

 or by experimental interference. One of the 

 most familiar of these, on account of its fre- 

 quent occurrence, is the change in the cha- 

 racter of the urine in cases of paraplegia ; 

 resulting, as it would seem, from the secre- 

 tion of an undue quantity of alkaline mucus 

 from the lining of the bladder.* Various ex- 

 periments have been made upon the nerves of 

 the kidney, which seem to indicate that the 

 normal secretion of urine is dependent upon 

 their integrity. Thus Krimerf states, that 

 division of any of the nerves of the kidney 

 occasioned albumen and the red colouring 

 matter of the blood to pass into the urine, 

 their proportion increasing as that of the re- 

 gular constituents of the urine diminished. 

 Division of the vagus did not put a stop to 

 the secretion of urine ; but rhubarb and 

 prussiate of potass taken by the mouth ceased 

 to pass off by the urine, which at the same 

 time acquired greater specific gravity from 

 containing serum of the blood. After divi- 

 sion of the spinal cord in the dorsal or lumbar 

 region, the urine became limpid like water; 

 and division of the sympathetic nerve in the 

 neck caused it to become alkaline and albu- 

 minous. Brachet and Miiller have both ex- 

 perimented on the effects of the division of 

 the sympathetic nerves which are distributed 

 upon the renal artery. The former divided 

 the trunk, and connected the divided ends by 

 a canula, so as to allow of the continued 

 passage of blood, whilst the nervous influence 

 was completely intercepted j the latter pro- 

 duced the same condition by applying a liga- 

 ture around the renal vessels, so tightly as to 

 destroy the texture of the renal nerves at 

 that point, and then relaxing it again, so as 

 to permit the re- establishment of the circu- 

 lation. In both cases the effect was similar ; 

 the secretion of true urine being interrupted, 

 but a sanguineous fluid passing into the 

 * The nature of this change has been elsewhere 

 considered. See Vol. III. p. 721 T. art. NERVOUS 

 SYSTEM. 



f Quoted in Muller's Physiology (Baly's Trans- 

 lation), p. 470. 



BBS 



