\\ IMPORTANT PART OF THE HOD^S RKFKICKKV I IN(. MM'VKMl S 



AmoTiK f)tlier functions, the sweat glands allow water to evaporate from the surface of the body, 

 thereby reducing its temperature in warm weather. The above model shows two con- 

 sjjicuous black hairs and between them (its mouth marked by an arrow at the top of the 

 jjicture) a sweat gland. From its opening on the surface, a fine tube which may be as much 

 as a third of an inch long runs down and ends in a coil, surrounded by ca])illary blood 

 vessels. Water from the Ijlood filters through the walls of these vessels into the sweat 

 gland and is discharged on the surface of the body. The tropical races, who have most 

 need to keep the body cool, are provided with many more sweat glands than are the 

 northern peoples — an example of their constitutional adaptation, through evolution, 

 to the climate in which they live. Photograph from Rcn6 Bache. (Fig. 7.) 



