458 THE HUMAN BODY. 



division of the spinal cord in two ways tends to lower the 

 temperature of parts below the injury: in the first place, 

 the muscles are paralyzed and so a great source of heat is 

 cut off; and in the second, the vaso-motor nerves traveling 

 down from the medullary centre are cut, and hence the 

 skin arteries behind the section dilate and carry more blood 

 to the surface to be cooled. To explain the rise of tem- 

 perature it has therefore been concluded that there are 

 true thermic centres in the spinal cord, which centres, like 

 others in that organ (Chap. XXXV.), are held in check or 

 inhibited by brain-centres; when the controlling influence 

 of the latter is removed the former may excite excessive oxida- 

 tions in the tissues to which they are distributed, and so 

 produce the rise of temperature. Recent calorimetric ex- 

 periments seem to prove that injury of certain regions of 

 the brain is followed by greatly increased heat production 

 in the Body: fever may be due to greater or less paralysis 

 of these centres. 



Clothing. To man, as social animal, endowed with 

 moral feelings, clothing has certain uses in the interests 

 of morality; but for such purposes the amount necessary is 

 not great, as we find in many tribes living in warm climates. 

 Except in tropical regions, however, clothing has in addi- 

 tion an important physiological use in regulating the bodily 

 temperature. While the majority of other warm-blooded 

 animals have coats of their own, formed of hairs or feathers, 

 over most of man's Body his capillary coating is merely rudi- 

 mentary and has lost all physiological importance; and so 

 he has to protect himself by artificial garments, which 

 his aesthetic sense has led him to utilize also for purposes of 

 adornment. Here, however, we must confine ourselves to 

 clothes from a physiological point of view. In civilized 

 societies every one is required to cover most of his Body 

 with something, and the question is what is the best 

 covering; the answer will vary, of course, with the climatic 

 conditions of the country dwelt in. In warm regions, 

 clothing, in general terms, should allow free radiation or 

 conduction of heat from the surface; in cold it should do 

 the reverse; and in temperate climates, with varying tem- 

 peratures, it should vary with the season. If the surface 



