48

ELEMENTS OF MATERIA MEDICA.

practical value in therapeutics. 1 We avail ourselves of this influence, and employ externa!heat tu produce determination of blood to, and augmented secretion of, the skin on various occa-sions; as when an internal malady is attended with coldness of surfaee, or appears to beconnected with the sudden disappearance of a cutaneons eruption. The benefit obtained bythe use of external heat in gastritis, enteritis, cystitis, and nephritis, is in part referrible Wthe same antagonizing influence. External heat is also an important adjuvant in the treat*nient of diabetes: it checks the excessive secretion of urine, and relieves the dry and unper-spirable State of the skin. Whenever we exhibit sudorific medicines, we proinote their Opera-tion by keeping the surfaee warm ; while when we employ diuretics, the skin should be kep'cool. The ageney of tropieal heat in weakening the digestive organs, and the efficaey ofspices, taken as eondiments, in counteracting this effect, are clearly referrible to the principleof antagonism above explained.

The augmented secretion of bile, and the tendency to hepatic diseases, socommonly observed in Europeans when they become residents in warm climates,are other effects of the continued Operation of heat on the body.

That heat, aidcd by inactivity, abundance of solid food, and little or no drink, is capable ofinducing hepatic disease, is well shown on the goose. The celebrated pätes de foies gras,prepared at Strasburg and Metz, are mude from the livers of geese artificially enlarged.These animals are crammed with food, kept from drink, nailed to a plank by the webs oftheir feet, and placed quite dose to a fire: and, in due time, their livera become greatlyenlarged.

Relaxation of the living tissues is another eonsequence of the employment ofmoderate heat. This effect, which is best observed when moisture is conjoinedwith caloric, commences first in the part to which heat is applied: and, whenthe whole surfaee of the body has been subjeeted to an increased temperature, itsrelaxing influence soon extends to internal parts: hence arise atony, diminutionof muscular power, a feeling of languor or fatigue, and an indisposition to cor-poral exertion.

We take advantage of this relaxing influence of heat in the treatment of spasmodic diseases,in the reduetion of dislocations, in the application of the taxis in hernia, and on many otheroccasions where our objeet is to relax or soften muscular or other tissues, On the other hand,we avoid the employment of heat where preternatural relaxation or atony of the general sys-tem, but especially of the surfaee, exists.

The primary effect of moderate heat on the nervous System is excitation; thesecondary effect, exhaustion. In the first instance sensibility is agreeably pro-moted, the action of the voluntary muscles assisted, and the intellect somewhatexalted. But to these effects sueeeed languor, relaxation, listlessness, indisposi-tion to corporal and mental labour, and tendency to sleep.

Lastly, the prevailing malaclies of hot climates may be referred to as fartherillustrations of the effect of continued heat on the body. Fevers, diarrheea, dys-entery, cholera, and liver diseases, may be regarded as the special maladies ofthe burning equatorial regions.

The exhaustion, which follows the excitation caused by heat and other Stimuli,would seem, to use the words of Müller, (Op. cit. vol. i. p. 52.) to " show thatthe organic force is consumed, as it were, by the exercise of the funetions;" andto employ a siroile of Dr. Priestley, 3 we may say, that as a candle burns outmuch faster in oxygen gas than in air, so we may be said to live out too fastwhen under the exciting influence of an elevated temperature.

Uses. —Heat is employed as a remedial agent for various purposes, of whichthe following are the prineipal:—

1. To cause an afflnx of blood to a part; by which,—

a. Healthy eirculation and temperature may be restored.

b. The equalization of the distribution of blood may be effected; and thereby a pre-

ternatural afflux to other organs checked.

c. The secretions and exhalations of a part may be re-established or increased.

2. To proinote the general eirculation of blood.

i See some valuable reniarks on the '* antagonUm" of the secretions, in Müller's Elements of Pkysiology, byDr. Baly, vol. i. p. 473.

a Experiments and Observaiions on different kinds of Air, vol. ii. p. 169. Birmingham, 179U.