232 PHYSIOLOGY FOR DENTAL STUDENTS. 



posit of calcium or magnesium phosphate. This will dissolve 

 when the urine is rendered faintly acid. 



ABNORMAL CONSTITUENTS OP THE URINE. Many of tin- sub- 

 stances found in the blood occur in minute traces in the urine. 

 When any of these bodies are increased to an unusual amount 

 in the urine, they become what we may term pathological con- 

 stituents. The bodies most commonly affected are the proteins 

 and sugars. The finding of a protein such as albumin, in more 

 than the faintest trace, is an indication of nephritis or Bright 's 

 disease. The presence of albumin may be detected by heating in 

 a test tube a slightly acidulated sample of urine. 



Normal urine contains the faintest trace of the blood sugar 

 dextrose, but in abnormal conditions, as in the disease dialxfis 

 or after a meal rich in sugars, a large amount of dextrose ap- 

 pears in the urine as a result of an increase in the sugar of the 

 blood. The condition probably represents the inability of the 

 tissues to make use of their carbohydrate food in the proper man- 

 ner, and the kidney therefore excretes the sugar as if it were a 

 waste material. 



The Organs of Excretion, The Kidneys. 



Projecting from the posterior wall of the abdominal cavity at 

 the level of the lower ribs and on each side of the vertebral col- 

 umn are the kidneys, the organs of urine excretion. Each kidney 

 is of the nature of a tubular gland of a very complex structure, 

 anatomically adapted to bring a large amount of blood at a high 

 pressure in close relation with the excreting epithelial cells which 

 line the walls of the gland tubules. The tubules empty into a 

 pouch-shaped sac on the inner edge of the kidney, the pelvis 

 of the kidney, and this is connected with the urinary bladder by 

 means of a small tube, the ureter. 



A brief review of the essential parts of the uriniferous tubule 

 and the organs of micturition is necessary in order to understand 

 the mechanism of urine excretion, and the student is advised to 

 consult his textbook of anatomy and histology for a more com- 

 prehensive description than is here given. The uriniferous tu- 

 bules may be divided into the excretory portion and the collect- 

 ing portion. The tubules arise in the outer part of the kidney. 



