468 



SECRETION. 



ureter. Miiller states that a remarkable 

 softening of the kidney was always one of the 

 results of these experiments. 



Numerous experiments have been made to 

 determine the degree of dependence of the 

 secretion of the gastric fluid upon the nervi 

 vagi ; to these experiments copious references 

 have elsewhere been given*, and we shall 

 therefore only here allude to their results. 

 The temporary suspension of the digestive 

 process appears to be an invariable result of 

 the complete division of the par vagum on 

 both sides ; and many of those who have 

 witnessed this result have somewhat hastily 

 concluded, that the secretion of gastric fluid 

 is dependent upon nervous agency conveyed 

 through that nerve. But it has been observed, 

 in several instances, that the digestive powers 

 have returned after a time, animals which 

 were becoming much emaciated having re- 

 covered their flesh ; and it is obvious, there- 

 fore, that the secretion of the gastric fluid can 

 not he dependent upon the supply of nervous 

 agency through the par vagum, as some have 

 supposed it to be. It is true, that in a large 

 proportion of the experiments made to deter- 

 mine this question, there has been no appear- 

 ance of any return of the digestive power, after 

 complete section of the par vagum on both 

 sides ; but there are various modes of account- 

 ing for this fact., The animals on which this 

 experiment has been made, usually live for 

 only a short time afterwards, on account of 

 the disorder of the respiratory processes, 

 which is one of the results of the operation ; 

 so that all which is proved by the great bulk of 

 the experiments is, that, the digestive process 

 is generally arrested during the short time that 

 the animal lives after the vagi have been di- 

 vided or tied. And such negative results, as 

 Dr. J. Reid has very justly observed, " can 

 never overthrow the results derived from 

 positive experiments, provided that these 

 have been accurately performed, and are free 

 from all sources of fallacy." f 



With these facts before us, it is much to be 

 desired that the experiments just cited, as to 

 the influence of section of the renal nerves 

 upon the secretion of the kidnev, had been 

 sufficiently prolonged to ascertain whether 

 the effects described are transient, and whether 

 the real secretion would be restored if time 

 were permitted. And it is obvious that as 

 they at present stand, no such experiments 

 can serve as an adequate foundation for the 

 hypothesis entertained by some, that the act 

 of secretion is dependent upon nervous in- 

 fluence, or, in other words, that nervous 

 agency supplies a condition without which it 

 cannot take place. 



There is another group of phenomena bear- 

 ing upon this question, though le.ss closely 

 related to it, namely the changes in the 

 state of nulrilion in parts whose nerves have 

 been injured, and which are thereby rendered 

 insensible. The close affinity, however, al- 

 ready shown to exist between the functions 



of Nutrition and Secretion, is sufficient to 

 make it apparent that they must stand upon 

 the same footing in this respect, and that 

 whatever is true as to the relation of either of 

 them to the nervous system, must be true also 

 of the other. Now it is an observation very 

 frequently made, that parts whose nerves have 

 been paralysed are peculiarly disposed to suffer 

 from destructive inflammation, or to undergo 

 a gradual wasting. The latter of these changes 

 is easily accounted for on the general principle 

 dwelt on under the head of NUTRITION, that 

 the degree of nourishment which any organ 

 or tissue receives, depends upon its functional 

 activity; and thus not merely the muscles, 

 but all the textures of a paralysed limb gradu- 

 ally waste away, the disuse of its muscles occa- 

 sioning a stagnation in the circulation through 

 the entire part. Of the former result it is ne- 

 cessary to make a careful examination, that 

 we may be prepared to estimate it at its true 

 value. One of the cases most frequently 

 quoted in this connection, is the effect of 

 section of the trigeminus in producing destruc- 

 tive inflammation of the eye-ball, as first shown 

 by Magendie, and confirmed by many sub- 

 sequent experimenters. A full account of 

 these effects has been already given in another 

 part of this work (see FIFTH PAIR), and it is 

 therefore unnecessary to repeat them here. 

 A corresponding result may be produced by 

 disease. A case is related by Mr. Stanley*, 

 in which there was impairment of the whole 

 nutrition of one side of the face, with frequent 

 attacks of erysipelatous inflammation, bleeding 

 from the nose, central penetrating ulceration 

 of the cornea, and, at last, destructive inflam- 

 mation of the tunics of the eye, in consequence 

 (as it would appear) of destruction of the 

 trunk of the trigeminal nerve of that side by 

 the pressure of a tumour near the pons. No 

 such destructive effects ensue on section of 

 any of the other cranial nerves ; the only 

 injurious influence exercised on the eye by 

 any such operation, being the tendency to 

 inflammation from irritants which the para- 

 lysed orbicularis palpebrarum does not shut 

 out or help to remove. But, on the other 

 hand, cases are occasionally to be met with (of 

 which the author has himself witnessed more 

 than one) of the complete paralysis of the 

 ophthalmic division of the fifth pair, which has 

 existed for some time without any other result 

 than a degree of dryness of the surface of the 

 eye from deficient secretion, and a disposition 

 to superficial inflammation from irritating par- 

 ticles of whose presence no warning was 

 given by sensation, and for whose removal 

 there was consequently no provision. Such 

 exceptional cases must be admitted as proving 

 that, however unfavourable may be division 

 or injury of the trigeminus to the continued 

 healthy nutrition of the eye, still this may be 

 maintained ; and that it is consequently no 

 more essentially dependent upon "nervous 

 influence," supplied through that channel, 

 than is the secretion of gastric fluid upon the 



Vol. III. p. 900. art. PAR VAGUM. f Ibid. 



* Medical Gazette, vol. i. p. 531. 



