296 A YEAR IN SCIENCE 



place of abode. Man lived in this way for thousands 

 of years. Remnants of the implements which he used 

 have been found, but we have no other records of the 

 history of primitive man. The earliest monuments and 

 inscriptions which we have date back more than six 

 thousand years. 



There exist upon the earth at present at least three 

 varieties of man. Each of these differs from the others 

 in external appearance, in instincts, and in social cus- 

 toms. These three varieties are : (1) The white or 

 Caucasian; (2) the yellow or Mongolian; (3) the black 

 or Ethiopian. To these are often added the brown or 

 Malay race of the islands of the Pacific, and the red 

 or American Indian. 



The human body. In our present study we are espe- 

 cially interested in man as he exists to-day. It is impor- 

 tant for each of us to know how the human body is 

 constructed (anatomy); what work, or function, each 

 part of the body must perform and how this is accom- 

 plished (physiology); and finally, how to care for the 

 body in such a way that all its parts are working- 

 normally, and consequently are in good health (hygiene). 



We can not properly care for the body unless we 

 know its structure and its functions. We often under- 

 estimate the value of such knowledge concerning the 

 parts of the body used in digesting the food, the struc- 

 tures used for admitting air, or getting rid of waste 

 materials. Such knowledge may be of great aid to us. 

 Health is wealth. It not only leads to material wealth, 



