1102 ANIMAL HEAT 



The Nervous Mechanism Regulating Thermotaxis. Technically 

 heat-production is designated as thermogenesis, heat-dissipation as 

 thermolysis, and the relationship between these two factors as thermo- 

 taxis. The question concerning the part which the nervous system 

 plays in thermotaxis, cannot be answered with certainty. We have 

 previously seen that reflexes producing vasomotor and secretomotor 

 changes, are constantly at play, and hence, it must be concluded that 

 the central nervous system is closely concerned with heat-regulation. 

 Thus, we find that the infant does not acquire this function until 

 some time after birth, while other animals, such as the guinea-pig 

 and chick, already possess it when they are born. In other words, 

 thermotaxis follows a course parallel to that of the development of the 

 nervous system, and this must necessarily be so, because the striated 

 and smooth muscle tissues and sweat-glands must first obtain their 

 innervation before they can be in a position to influence the body-tem- 

 perature. Some doubt, however, still exists regarding the presence 

 of separate heat-centers and heat-nerves. For all that matt-rs, 

 every motor nerve of skeletal muscle may really be regarded as a heat- 

 nerve and every nucleus as a heat-center, because the impulses 

 generated by them not only influence muscular activity but also 

 their production of heat. Consequently, the condition existing here, 

 is very similar to that previously observed in the case of the trophic 

 nerves, when we came to the conclusion that the nutritive state of a 

 tissue is dependent upon the ordinary motor impulses relegated to it, 

 and not upon separate impulses of a purely trophic kind. 



Many observers have found that injuries to various parts of the 

 cerebral cortex, basal ganglia, and medulla give rise to changes in the 

 body-temperature. Thus Krehl, Ott, 1 Reichert, 2 and others, have 

 noted that the transverse division of the corpora striata invariably pro- 

 duces a pronounced rise in the body-temperature (110 F.) and death. 

 Other heat-accelerator centers have been localized in the tuber cinereum, 

 cruciate sulcus, and the juncture of the suprasylvian and postsylvian 

 fissures. Heat-inhibitory centers have been localized in the medulla 

 and region of the pons. The evidence at our disposal, however, is 

 too meager to warrant definite conclusions, because many errors have 

 undoubtedly crept in on account of the character of the methods 

 which must necessarily be practised in experiments of this kind. The 

 latter consist in the destruction of parts, transection of paths, cauter- 

 ization and puncture. Secondly, it is very possible that the results 

 of these procedures are dependent in a large measure upon disturbances 

 of the vasomotor (tuber cinereum) and musculomotor mechanisms 

 (medulla), and not upon a derangement of the function of true heat- 

 centers. 



1 Jour. Nerv. and Mental Dis., 1884. 



2 Univ. Penna. Med. Magazine, 1894; also White, Jour, of Physiol., xii, 1891, 

 233; Tangl, Pfltiger's Archiv, 1895; and Sachs and Green, Am. Jour, of Physiol., 

 xlii, 1917, 603. 



