79 



and it is much less. patiently endured. If it be not satisfied, the blood, and 

 the fluids which are formed from it, become more and more stimulating, 

 from the concentration of the saline and other substances which they con- 

 tain. The genera! irritation gives rise to an acute fever, with heat and 

 parching of the fauces, which inflame, and may even become gangrenous, 

 as happens in some cases of hydrophobia. English sailors, who were 

 becalmed, had exhausted all their stock of fresh water, and were at a dis- 

 tance from land; not a drop of rain had for a long time cooled the at- 

 mosphere: after having borne, for some time, the agonies of thirst, fur- 

 ther increased by the use of salt provisions, they resolved to drink their 

 own urine. This fluid, though very disgusting, allayed their thirst; but 

 at the end of a few days, it became so thick and acrid, that they were in- 

 capable of swallowing a mouthful of it. Reduced to despair, they expect- 

 ed a speedy death, when they fell in with a ship which restored them to 

 hope and life. Thirst is increased every time that the aqueous secretions 

 are increased; thus, it becomes distressing to a dropsical patient, in 

 whom the fluids are determined towards the seat of effusion. It is ex- 

 cessive in diabetes, and in proportion to the increased quantity of urine. 

 In fever, it is increased, from the effect of perspiration, or because in 

 some of these affections, for example in bilious fevers, the blood seems 

 to become more acrid. Hence the advantage of cooling, diluting, and 

 refreshing drinks, administered copiously, with a view to correct the 

 temporary acrimony occasioned by the absence of a great quantity of the 

 serous parts of the blood, and to lessen the over excitement of a fluid be- 

 come too stimulating. 



The use of aqueous drink is not the most effectual method of allaying 

 thirst. A traveller exposed to the scorching heat of summer, finds it ad- 

 vantageous to mix spirits to plain water, which alone does not stimulate 

 sufficiently the mucous and salivary glands, whose secretion moistens 

 the inside of the mouth and pharynx, and covers these surfaces with the 

 substance best calculated to suspend, at least for a time, the erethism on 

 which thirst appears to depend. 



VI. On Mastication*. The organs employed in the mastication of the 

 food, are the lips, the jaws, and the teeth; with these are furnished, the 

 muscles by which they are moved, and those which form the parietes of 

 the mouth. The motions of the lips are extremely varied, and depend on 



evince the deleterious effects of these substances upon the animal economy : hence the 

 state of these organs is an important index to the condition of the circulating fluids, and 

 of the whole system, in a number of diseases. 



Those physiologists who refer the operations of the livingbody to a galvanic process, 

 carried on by the nervous system on the fluids contained in the vascular, especially in 

 the capillaries, assign, as the proximate causes of thirst, a deficiency of oxygen and an 

 abundance of the inflammable materials amongst these elements which constitute the 

 fluids circulating at the time in which the sensation is induced, (" Oxygenii autem de- 

 fectum et phlogisticorum abundantium sitim adducere.") This, or a similar opinion, is 

 entertained by SPHENGEI,, PROCHASKA, BCIIBACH, and LENHOSSECK. The arguments 

 which these systematic writers on physiology adduce, as well as the experiments of 

 Dr. PHILIP, in support of the theory which ascribes the vital phenomena to galvanic 

 processes taking place in the system, deserve to be calmly considered before they are 

 designated to be either visionary or untenable. Copland. 



* The following operations are comprehended under the process of digestion, name- 

 ly, 1. mastication ; 2. insalivation ; 3. deglutition ; 4. the action of the stomach ; 5. the 

 action of the small intestines; 6. the action of the large intestines; 7. the expulsion of 

 the faeces Copland, 



