286 DISEASES SECT. XXXII. 3. 2. 



atmofphere of heat, in which all things are immerfed, and the 

 other from the internal combinations of the particles, which 

 form the various fluids, which are produced in the extenfive 

 fyftems of the glands. When either the external heat, which 

 furrounds us, or the internal production of it, becomes leflened 

 to a certain degree, the pain of cold is perceived. 



This pain of cold is experienced moft fenfibly by our teeth, 

 when ice is held in the mouth ; or by our whole fyftem after 

 having been previoufly accuflomed to much warmth. It is 

 probable, that this pain does not arife from the mechanical or 

 chemical effects of a deficiency of heat ; but that, like the or- 

 gans of fenfe by which we perceive hunger and thirft, this fenfe 

 of heat fuffers pain, when the ftimulus of its objeft is wanting 

 to excite the irritative motions of the organ ; that is, when the 

 fenforial power becomes too much accumulated in the quiefcent 

 fibres. See Sect. XII. 53. For v as the periftaltic mottbns of 

 the ftomach are leflened, when the pain of hunger is great, fo 

 the action of the cutaneous capillaries are leflened during the 

 pain of cold ; as appears by the paienefs of the fkin, as explain- 

 ed in Seel:. XIV. 6. on the production of ideas. 



The pain in the fmall of the back and forehead in the cold 

 fits of the ague, in nervous hemicrania, and in hyfteric parox- 

 yfms, when all the irritative motions are much impaired, feems 

 to arife from this caufe : the veflels of thefe membranes or 

 mufcles become torpid by their irritative aflbciations with other 

 parts of the body, and thence produce lefs of their accuftomed 

 fecretions, and in confequence lefs heat is evolved, and they 

 experience the pain of cold ; which coldnefs may often be felt 

 by the hand applied upon the afFe&ed part. 



2. The importance of a greater or lefs dedu&ion of heat 

 from the fyftem will be more eafy to comprehend, if we firft 

 confider the great expenfe of fenforial power ufed in carrying 

 on the vital motions , that is, which circulates, abforbs, fecretes, 

 aerates, and elaborates the whole mafs of fluids with unceafing 

 afliduity. The fenforial power, or fpirit of animation, ufed in 

 giving perpetual and ftrong motion to the heart, which over- 

 comes the elafticity and vis inertix of the whole arterial fyftem ; 

 next the expenfe of fenforial power in moving with great force 

 and velocity the innumerable trunks and ramifications of the 

 arterial fyftem ; the expenfe of fenforial power in circulating 

 the whole mafs of blood through the long and intricate intor- 

 tions of the very fine veflels, which compofe the glands and 

 capillaries ; then the expenfe of fenforial power in the exer- 

 tions of the abforbent extremities of all the la&eals, and of all 

 the lymphatics, which open their mouths on the external fur- 

 face 



