THE SKIN AND KIDNEYS 



, set of tubes called the kidneys. The waste mineral matter 

 of the body also passes off by the skin and kidneys. 



205. The kidneys. The kidneys are two bean-shaped 

 bodies, lying one on each side of the backbone, underneath 

 the lowest ribs. Each kidney is made of coils of very fine 

 tubes lined with epithelial cells. These cells separate 

 the urea, mineral matters, and water from the blood, 

 and pour the whole into a single tube which goes to the 

 bladder. 



206. Urea in the perspiration. The perspiratory glands 

 of the skin also separate urea, mineral matter, and water 

 from the blood. The kidneys get rid of many times as 

 much urea and mineral matters as the skin, but the skin 

 gives off nearly as much water as the kidneys. Some- 

 times the kidneys get diseased, so that they cannot get rid 

 of the urea. Then the whole body is poisoned, and the 

 kind of disease called Bright 's disease comes on. Then 

 the skin may give off much more than its natural amount 

 of urea, until the kidneys are able to do their work again. 



207. Need of bathing. The water of perspiration dries 

 off from the skin and leaves the urea and mineral matters 

 behind. The outside of the epithelium becomes dead, and ' 

 part is worn off, and part stays upon the skin. All kinds' 

 of dust and dirt also stick to the skin, and stop its glands 

 so that the waste matters cannot pass off as they should. 

 So the skin needs to be bathed. Owing to the oil in the 

 skin, water alone will not always remove the dirt, and so 

 plenty of soap is needed. When there is an unpleasant 

 odor about the skin, it certainly needs a bath. 



In summer, when we perspire and the air is full of dust, 

 we need a bath more often than in winter. It does not 

 matter how the bath is taken, so long as we wash well. 

 We can get clean by using a common basin. Bathing the 



