SPECIAL PHYSIOLOGY. 



but it may also yield a ready fuel or combustible substance, easily ab- 

 sorbed into the system and easily oxidized in it; these two last-named 

 qualities may account for its great use in cases of exhaustion from 

 fevers. Again, when the sympathetic nerve is divided in the neck 

 of an animal, or its chief cervical ganglion is removed, the tempera- 

 ture of the whole of that side of the face may rise even as high as 11 

 above its normal standard; and this may continue for months with in- 

 creased sensibility and increased color from vascular congestion. In 

 such a case, when the distal end of the cut nerve is galvanized, the 

 temperature for a time falls. (Bernard.) The elevation of local tem- 

 perature is also believed to be an indirect effect, and to depend on an 

 increase in the flow of blood to the part, consequent upon a relaxation 

 of the walls of the smaller arteries, owing to the loss of controlling 

 power on the part of the vasi-motor nerves (p. 308). Serious injury, 

 or disease of the spinal cord may act in the same way, because the 

 sympathetic system has connections with, or origins in, it (p. 309). 

 The lowering of the temperature, after destruction of the brain, which 

 continues in spite of artificial respiration, not performed too rapidly, 

 so as to cool the animal by that very process (Brodie), but more slowly 

 (Wilson Philip and Williams), has also been, of late, most frequently 

 attributed to the loss of some indirect influence of the nervous system 

 over the strictly chemical heat-producing changes in the system, 

 whether of respiration, nutrition, or secretion. Lastly, it has been 

 suggested that heat may be directly produced in the nervous substance 

 itself, owing to the rapid metamorphoses to which it seems liable in its 

 healthy and active condition, or else to some transformation or passage 

 of its ordinary force or mode of action into a calorific action producing 

 heat, in the same manner, as in the electric fish, it may be converted 

 into electricity. (Carpenter.) The nervous substance must be decom- 

 posed in all cases in which it is in action, especially during exercise, 

 when it controls the muscular movements: much movement always 

 produces heat. In such instances, and also in psychical acts, the 

 nervous substance is directly oxidated ; so that, ultimately, the animal 

 heat evolved is the result of chemical action. 



That the nervous system is not essential to the production of heat 

 in living organisms, seems to be shown by the facts, that in many of 

 the lower animals no traces of a nervous system have yet been dis- 

 covered, and, that in certain processes of vegetable life, as in the fer- 

 tilization of the ovule, and in the commencing stages of germination, 

 heat is also evolved. When, however, in animals, that system is pres- 

 ent, it is endowed with such power of control over all the functions 

 generally, and exhibits such innate activity, that it determines and 

 excites waste in other tissues, and undergoes waste in its own, thus 

 indirectly or directly contributing to the production of animal heat. 



Uses of Animal Heat. 



The modes in which the heat of the body is expended are several. 

 First, it supplies the constant loss of heat from the body, by radiation 

 and conduction to the clothes or other surrounding objects or media, 



