VASO MOTOR CONTROL OF TEMPERATURE. 855 



vessels, the difference between the temperature of the skin and its 

 surroundings is increased, and likewise the loss of heat. Thus the first 

 effect of a warm bath may be a fall in the temperature of the internal 

 parts. The loss of heat by this flushing of the skin with hot blood and 

 by sweating may be very great, as shown by the rapid fall in tempera- 

 ture during the sweating state of ague or the crisis of pneumonia. 



These changes in the calibre of the vessels can be brought about 

 reflexly, not only by sensations of heat and cold but by those of pain ; 

 further, emotions can effect these changes, as in the blushing of excite- 

 ment or shame, and the pallor of fright or anger ; in fact, emotions may 

 in different individuals have opposite effects upon the vascularity of the 

 skin. 



An impression conveyed by the sensory nerves of one part of the 

 body can influence the calibre of the vessels, not only on the same side 

 but also on the opposite side. Thus, Brown-Sequard and Tholozan, 1 found 

 that plunging one hand in warm water raised the temperature of the 

 opposite hand also. Waller, 2 however, has failed to confirm this. 



The explanation of the part played by the vasomotor nerves in 

 the regulation of temperature is not so simple as may appear from a 

 first consideration, for the problem is complicated by the fact that 

 an increase or decrease in the vascularity of the skin is accom- 

 panied by a similar change in the production of sweat ; further, it is 

 possible that the alterations in vascularity may affect the metabolism 

 of the tissues. Upon this latter point there has been considerable dis- 

 cussion. The first and most important experiment in this connection 

 is that of Bernard, 3 who found that section of the cervical sympathetic 

 caused a dilatation of the blood vessels and a rise of temperature in the 

 ear of the same side. The enlargement of the blood vessels results in a 

 greater and more rapid flow of blood through the ear, and this would 

 naturally raise the temperature of the part. Bernard, however, did not 

 look upon this explanation as complete ; he held that the nervous 

 system regulated not only the circulation but also the production of 

 heat in the tissues, for he states, among other arguments, that section of 

 the cervical sympathetic, after previous ligature of the veins of the ear, 

 still caused a rise of temperature. According to Bernard, the nerve was 

 both vaso-constrictor and frigorific. It was to be expected, however, 

 that this view would be contested, for although a certain amount of 

 heat would be produced in the ear, as in the metabolism of all tissues, 

 yet that amount would be small, for the cartilage and other tissues of 

 the ear are not the seats of an active exchange of material. 



Numerous experimenters 4 have decided against Bernard's theory, and 

 have attributed the changes in the temperature of the ear to alterations 



1 Journ. de I'anat. et physiol. etc., Paris, 1858, tome i. p. 497. 



2 Note communicated to the writer. 



3 "Le9ons sur la physiologic et la pathologic du systeme nerveux," 1858, tome ii. 

 p. 490 ; "Lecons sur la chaleur animale," 1876, p. 297. 



4 Brown-S'e'quard, Med. Exam., Philadelphia, 1852, p. 489, and 1853, p. 9 ; Budge, 

 Compt. rend. Acad. d. sc., Paris, tome xxvi. p. 337; Ztsclir. r. d. Vcrein f. Heilk. in 

 Preussen, 1853, Bd. xxii. S. 149; Waller, Compt. rend. Acad. d. sc., Paris, 1854, 

 tome xxxvi. p. 378: De Ruyter, " De actione atropfe belladonna?," Diss., 1853; Schiff, 

 "Untersuch. z. Physiol. des Nervensystems," 1855, Bd. i. S. 124 ; AUg. Wien. med. Ztg., 

 1859, S. 318 ; Kiissmaul and Tenner, Untersuch. z. Naturl. d. Mensch. u. d. Thiere, 

 1855, Bd. i. S. 92 ; Callenfels, Ztschr. f. rat. Med., 1858, Bd. vii. S. 157 ; Jacobson and 

 Landre, Nederl. Tijdschr. v. Geneesk.,^ Amsterdam, Bd. i. Heft 3 ; Donders, Wunderlich's 

 " Medical Thermometry," p. 148; Bayliss and Hill, Journ. Physiol, Cambridge and London, 

 1894, vol. xvi. p. 351. 



