316 INFLUENCE OF THE NERVOUS SYSTEM 



of a separate ganglionic system. It is by nervous influence, that the mucous 

 secretion covering the membranes is caused to be regularly formed for their 

 protection ; for it is shown by pathological facts, that, when this influence is 

 interrupted, and the secretion is no longer supplied, the membrane, losing its 

 protection, is irritated by the air or the fluids with which it may be in contact, 

 and passes into an inflammatory condition. This is the explanation of the 

 fact, which has been well ascertained, that the Eye is liable to suppurate when 

 the Fifth pair has been divided ; and that the mucous membrane of the Blad- 

 der becomes diseased in Paraplegia. 



426. The influence of particular conditions of the mind, in exciting vari- 

 ous Secretions, is a matter of daily experience. The flow of Saliva, for exam- 

 ple, is stimulated by the idea of food, especially that of a savoury character. 

 The Lachrymal secretion, again, which is continually being formed to a small 

 extent, for the purpose of bathing the surface of the eye, is poured out in great 

 abundance under the moderate excitement of the emotions either of joy, ten- 

 derness, or grief. It is checked, however, by violent emotions ; hence in intense 

 grief the tears do not flow. It is a well-known proof of moderated sorrow, 

 when this takes place ; tears, however, do not bring relief, as is commonly 

 believed, but they indicate that it has been brought. Violent emotion may also 

 suspend the Salivary secretion ; as is shown by the well-known test, often 

 resorted to in India, for the discovery of a thief amongst the servants of a family, 

 that of compelling all the parties to hold a certain quantity of rice in the 

 mouth during a few minutes, the offender being generally distinguished by 

 the comparative dryness of his mouthful, at the end of the experiment. The 

 influence of the emotion of love-of-offspring, in increasing the secretion of 

 Milk, is weil known. The formation of this fluid is continually going on 

 during the period of lactation ; but it is greatly increased by the sight of the 

 infant, or even by the thought of him, especially when associated with the idea 

 of suckling; this gives rise to the sudden rush of blood to the gland, which is 

 known by nurses as the draught, and which occasions a greatly increased 

 secretion. The strong desire to furnish milk, together with the irritation of the 

 gland through the nipple, has often been effectual in producing the secretion 

 in girls and old women, and even in men ( 683). The quantity of the Gastric 

 secretion is increased by exhilaration; at least if we may judge from the in- 

 crease of the digestive powers under such circumstances. Freedom from 

 mental anxiety favours the secretion of fat ; whilst continual solicitude effectu- 

 ally checks the disposition. It has been stated that total despair has an equal 

 tendency, with absence of care, to produce this effect ; persons left long to pine 

 in condemned cells, without a shadow of hope, frequently becoming remarka- 

 bly fat, in spite of their slender fare.* The odoriferous secretion of the Skin, 

 which is much more powerful in some individuals than in others, is increased 

 under the influence of certain mental emotions (as fear or bashfulness), and 

 commonly also by sexual desire. The Sexual secretions themselves are strongly 

 influenced by the condition of the mind. When it is frequently and strongly 

 directed towards objects of passion, these secretions are increased in amount, to 

 a degree which may cause them to be a very injurious drain on the powers of 

 the system. On the other hand, the active employment of the mental powers 

 on other objects, has a tendency to render less active, or even to check alto- 

 gether, the processes by which they are elaborated.! 



* Fletcher's Physiology, Part II., b, p. 11. 



f This is a simple physiological fact, but of high moral application. The Author 

 would say to those of his younger readers, who urge the wants of Nature as an excuse 

 for the illicit gratification of the sexual passion, " Try the effects of close mental 

 cation to some of those ennobling pursuits, to which your profession introduces you, i 

 combination with vigorous bodily exercise (for the effects of which see 278) ; befor 



; 



