EXCRETION 393 



Wastes given off by the Blood in the Kidney. — In the glomerulus 

 the blood loses by osmosis, through the very thin walls of the 

 capillaries, first, a considerable amoimt of water (amounting to 

 nearly three pints daily) ; second, a nitrogenous waste material 

 known as urea; third, salts and other waste organic substances, 

 uric acid among them. 



These waste products, together with the water containing them, are 

 known as urine. The total amount of nitrogenous waste leaving the body 

 each day is about twenty grains ; this is nearly all accounted for in the urea 

 passed off by the kidney, as urine is secreted in the kidney. It is passed 

 through the ureter to the urinary bladder; from this reservoir it is passed 

 out of the body, through a tube called the urethra. After the blood has 

 passed through the glomeruli of the kidney it is purer than in any other 

 place ui the body, because, before coming to the kidney, the blood lost a 

 large part of its burden of carbon dioxide in the lungs. After leaving the 

 kidney it has lost much of its nitrogenous waste. So dependent is the 

 body upon the excretion of its poisonous material that, in cases where the 

 kidneys do not do their work properly, death may ensue within a few hours. 



* 



Effect on the Kidneys. — It is said that alcohol is one of the 

 greatest causes of disease in the kidneys. The forms of disease 

 known as '* fatty degeneration of the kidney '' and " Bright's 

 disease " are both frequently due to this cause. The kidneys are 

 the most important organs. for the removal of nitrogenous waste. 



Alcohol unites more easily with oxygen than most other food 

 materials, hence it takes away oxygen that would otherwise be 

 used in oxidizing these foods. Imperfect oxidation of foods causes 

 the development and retention of poisons in the blood which it 

 becomes the work of the kidneys to remove. If the kidneys 

 become overworked, disease will occur. Such disease is likely to 

 make itself felt as rheumatism or gout, both of which are believed 

 to be due to waste products (poisons) in the blood. 



'' Influence of Alcohol upon Excretion. — If the waste sub- 

 stances constantly formed in the body are not promptly removed, 

 they tend to poison the system. When the organism is at a high 

 level of health, the breaking down of tissue by oxidation, which 

 produces waste, goes on rapidly and vigorously. When this is 

 retarded, as we have seen it to be when alcohol is introduced into 



