1T2 



ON THE EXTERNAL SENSES 



\Vhat is the cause of those peculiar sensations which we denominate 

 hunger and thirst ? A thousand theories have been advanced^to account 

 for them, but all have proved equally unsatisfactory, and have died one 

 after another almost as soon as they have received a birth. We trace 

 indeed the organs m which they immediately reside, and know by the sen- 

 sations themselves that the one exists in the region of the stomach, and the 

 other in that of the throat : but though we call them sensations, they 

 have neither of them any of the common characters of touch, taste, hear- 

 ing, seeing, or smelling. 



Foods and drinks are the natural and common means of quieting their 

 pain, but there are other means that may be also employed for this pur- 

 pose, and which are often found to answer as a temporary substitute : as, 

 for instance, pressure against the coats of the stomach in the case of hun- 

 ger, and stimulating the salivary glands in the case of thirst. It is hence 

 that chewing a mouthful of hay alone, or merely moistened with water, 

 proves so refreshing to a tired horse, and is found so serviceable when we 

 dare not allow him to slake his thirst by drinking. Savages and savage 

 beasts are equally sensible of the advantage of pressure in the case of 

 hunger, and resort to it upon all occasions in which they cannot take off 

 the pain in the usual way. 



The manis or pangolin tribes, that swallow their food whole, will swal- 

 low stones or coals or any other substance, if they cannot obtain nutri- 

 ment : not that their instinct deceives them, but for the purpose of acqui- 

 ring such a pressure as may bliint the sense of hunger, which is found so 

 corroding. Almost all carnivorous beasts pursue the same plan ; and a 

 mixture of pieces of coal, stone, slate, and earth, is often met with in the 

 stomach of ostrichs, cassowaries, and even toads. The Kamschadale 

 obtains the same purpose by swallowing saw-dust ; and some of the north- 

 ern Asiatic tribes by a board placed over the region of the stomach, and j 

 tightened behind with cords, in proportion to the severity of the suffering.! 

 Even in our own country we often pursue the same end by the same means ; 

 and employ a tight handkerchief, instead of a tightened stomach-board. 



In consequence of this difference in the mode in which the matter of 

 touch or general feeling is secreted under different circumstances, we 

 may also perceive why some parts of the body, although perhaps as largely 

 furnished with the nerves of touch or general feeling as other parts, are 

 far less sensible and irritable ; as the bones, the teeth, and the tendons; 

 and why the very same parts should, under other circumstances, as when 

 morbidly affected, become the most sensible or irritable of all the organs 

 of the system ; a fact well known to all, but I believe not hitherto satis- 

 factorily accounted for by any one. 



We may also see why inflammation, attacking different organs of the 

 body, should be accompanied with very different sensations. In the bones 

 and cartilages, except in extreme cases, it is accompanied with a dull and 

 heavy pain ; in the brain, with an oppressive and stupifying pain ; and in 

 the stomach, with a nauseating uneasiness. So, again, in the skin, mus- 

 cles, and cellular membrane, it is a pain that rouses and excites the system 

 generally ; but in those parts which are supplied with the two branches 

 of nerves which are called par vaguni and sympathetic, as the loins and 

 kidneys, the patient is affected with lowness of spirits from the first 

 attack of the inflammation.* 



/ 



* HimfpT on Blood, p. 289, 290. 



