76 OUR BODIES AND HOW WE LIVE 



An iron salt is found in very small quantities in many of 

 the foods we eat. It helps make good blood. Sulphur is 

 obtained from the yolk of eggs. 



112. Water. Drink is of just as much importance as 

 solid food. Every one knows what happens to plants 

 when they are deprived of water. They first droop and 

 then soon afterwards wither and die. So also it is with 

 all animals. If they are deprived of their drink, they also 

 droop and at last die. 



Water is the agent which has been provided by nature to 

 wash the food through the living tissues. Wild animals, 

 as well as domestic, take no other drink but water. Pure 

 water is the only drink that is absolutely essential for good 

 health. Thousands of human beings, following the exam- 

 ple of the lower animals, drink nothing but water, but yet 

 toil long and hard and keep well and strong. 



To be suitable for drinking, water should be clear, with- 

 out color, with little or no taste or smell, and free from any 

 great amount of animal or vegetable matter. 1 



1 There is a definite group of diseases which are especially liable to be 

 spread by means of bacteria in drinking water. Among these are such 

 diseases as typhoid fever and cholera. 



The appearance of the water is by no means conclusive, for it may be 



beautifully clear and palatable, yet 

 contain m y riads of deadl 7 bacteria; 



or k may be muddv and of a disa s ree - 



able odor and taste, and yet contain 

 nothing of a really harmful nature. 

 The only way by which absolute cer- 

 tainty can be had lies in a chemical 

 and bacteriological analysis, repeated 

 FIG. 54. A Group of the More Com- at regular intervals. 



mon Bacteria found in Water. No water at our command upon 



the surface of the earth is absolutely 



free from bacteria. Spring water is the purest, and -water from deep arte- 

 sian wells is about equally pure, Water from lakes and reservoirs is next 



