600 AN AMERICAN TEXT-BOOK OF PHYSIOLOGY. 



lytic. In classifying thermogenic centres we would regard the centre as being 

 a general thermogenic centre if it is capable, after the destruction of other 

 thermogenic centres, of causing the normal output of heat ; a thermo-acceler- 

 ator centre is distinguished by the fact that excitation increases thermogenesis, 

 while destruction does not diminish thermogenesis, unless the centre happens 

 to be active at the time, and further by the fact that after its destruction the 

 normal output of heat may continue ; a thermo-inhibitory centre is distinguished 

 by a decrease of heat-production following stimulation and by the absence of 

 any permanent effect on thermogenesis when the centre is destroyed. The 

 general or reflex thermogenic centres are undoubtedly continuously active, the 

 degree of activity varying according to the immediate demands of the organism 

 for heat ; while the therm o-accelerator and thermo-inhibitory centres are prob- 

 ably only intermittently active, coming into play when the general centres are 

 of themselves unable to effect a sufficiently rapid compensation. 



While it must be admitted that our knowledge of the precise locations, 

 physiological peculiarities, and correlations of the thermogenic centres is by no 

 means complete, we have at our disposal some most important and significant 

 data. The general thermogenic centres have been shown by Reichert l to be 

 located in the spinal cord. The thermogenic centres in the brain are either 

 thermo-accelerator or thermo-inhibitory. Thermo-accelerator centres probably 

 exist in the caudate nuclei (possibly also in the tuber cinereum and optic 

 thalami), pons, and medulla oblongata. 2 



Excitation of any one of these regions is followed by a pronounced rise of 

 heat-production ; destruction of any one region may or may not be followed 

 by a decrease of heat-production, and if a decrease does occur it may in most 

 cases be attributed to incidental causes, such as shock and other attendant 

 conditions. The centre which is common to the pons and medulla is for the 

 most part probably located in the latter, but it is not so powerful in its influ- 

 ences on thermogenesis as the thermo-accelerator centres in the basal regions 

 of the cerebrum. These cerebral centres are affected by agents which have 

 little or no effect on the heat centres of the spinal cord. Thermo-inhibitory 

 centres have been located in the dog in the region of the sulcus cruciatus and 

 at the junction of the supra-Sylvian and post-Sylvian fissures. 3 Irritation 

 of either of them is followed by a decrease of heat-production, while their 

 destruction may be followed by a transient increase of heat-production. The 

 cruciate centre is the more powerful. None of these cerebral centres exercises 



1 University Medical Magazine, 1894, vol. v. p. 406. 



2 Reichert: University Medical Magazine, 1894, vol. 6, p. 303. Ott : Journal of Nervous and 

 Mental Diseases, 1884, vol. 11, p. 141; 1887, vol. 14, p. 154; 1888, vol. 15, p. 85; Therapeutic 

 Gazette, 1887, p. 592; Fever, Thermotaxia, and Calorimetry, 1889. Aronsohn and Sachs: Pfliiger's 

 Archiv fur Physiologie, 1885, vol. 37, p. 232. Girard : Archiv de Physiologie normale et patholo- 

 gigue, 1886, vol. 8, p. 281. Baginsky und Lehmann : Virchow's Archiv fur Pathologic, 1886, Bd. 

 106, p. 258. White: Journal of Physiology, 1890, vol. 11, p. 1 ; 1891, vol. 12, p. 233. Baculo: 

 Centri temici, 1890, 1891, and 1892. Tangl: Pfliiger's Archiv fur Physiologie, 1895, vol. 68, p. 559. 



3 Wood: "Fever," Smithsonian Contributions to Knowledge, 1880, No. 357. Ott: Journal of 

 Nervous and Mental Diseases, 1888. 



