QUANTITY OF CUTANEOUS EXHALATION 319 



the cervical region of the cord, for the anterior extremities. According 

 to Adamkiewicz, these centres are subordinate to the principal sweat- 

 centre, which is situated in the bulb. Ott has collected a number of 

 cases of disease of the cord in the human subject which go far to con- 

 firm the results of experiments on the inferior animals in regard to the 

 action of excito-secretory nerves and sweat-centres. 



When the skin is in a normal condition, after exercise or whenever 

 there is a tendency to elevation of the animal temperature, there is 

 a determination of blood to the surface, accompanied with an increase 

 in the secretion of sweat. This is the case when the body is exposed 

 to a high temperature; and it is by an increase in the transpiration 

 from the surface that the heat of the body is kept down to a normal 

 standard. 



Quantity of Cutaneous Exhalation. The quantity of cutaneous ex- 

 halation is subject to variations, depending on conditions of temperature 

 and moisture, exercise, the quantity and character of the ingesta etc. 

 Most of these variations relate to the action of the skin in regulating the 

 temperature of the body; and it is probable that the elimination of ex- 

 crementitious matters by the skin is not subject, under normal condi- 

 tions, to the same modifications, although experiments on this point are 

 wanting. When there is such a wide range of variation in different in- 

 dividuals and in the same person under different conditions of season, 

 climate etc., it is possible to give only approximate estimates of the 

 quantity of sweat secreted and exhaled in the twenty-four hours. It is 

 assumed, however, that the average quantity is nearly two pounds, or 

 about 900 grams. 



Under violent and prolonged exercise, the loss of weight by exhala- 

 tion from the skin and lungs may become very considerable. It is 

 stated by Maclaren, the author of a work on training, that in one hour's 

 energetic fencing, the loss by perspiration and respiration, taking the 

 average of six consecutive days, was forty ounces (1130 grams), with a 

 range of variation of eight ounces (227 grams). 



When the body is exposed to a high temperature, the exhalation 

 from the surface is largely increased ; and it is by this rapid evapora- 

 tion that persons have been able to endure for several minutes a dry 

 heat considerably exceeding that of boiling water. Southwood Smith 

 made a series of observations in regard to this point on men employed 

 about the furnaces of gas-works and exposed to intense heat ; and he 

 found that in an hour the .loss of weight was two to four pounds (907 

 to 1814 grams), chiefly by exhalation of watery vapor from the skin. 

 In such instances the loss of water by transpiration is compensated by 

 the ingestion of large quantities of liquid. 



