tissues of the subcutaneous layer, these deep cutaneous capillaries radiate much less
heat to the surface.
(2) If the exposed surface area is reduced, there will be less loss of body
heat. This can even serve as a lifesaving measure. For example, if an individual has
been in cold water (as in a shipwreck or other accident), his body can be folded to
c. Shivering. During shivering, muscles contract without synchronization.
Although this produces minimal motion, it produces considerable heat.
d. Proper Clothing. Obviously, proper clothing is a measure for conserving
e. External Heat Sources. External heat sources are commonly used by
humans to conserve body heat.
Section VIII. VITAMIN D PRODUCTION
Vitamin D is a fat-soluble vitamin. It is required by the body in relation to calcium
3-33. MECHANISM OF PRODUCTION
The human body produces vitamin D in the integument. An organic compound
known as ergosterol is converted into vitamin D by ultraviolet solar radiation.
3-34. CONTROL OF PRODUCTION
Excessive production of vitamin D can become lethal to a human being. The
main purpose of skin pigmentation seems to be the limitation of vitamin D production.
In their "original" distribution, the peoples of the equatorial (sunny) areas tended to be
dark skinned. The peoples of subarctic (unsunny) areas tended to be light skinned.