8 



ing the tubules must have first passed through the glomeruli, 

 and is therefore more concentrated; in certain portions of the 

 tubules short cylindrical epithelial cells are found which are 

 comparable to true secreting cells found in other glands; and 

 finally, the smaller size of the efferent as compared with the 

 afferent vessel fulfills a condition which retards the flow of 

 blood through the glomerulus. 



The conditions are favorable for a high and variable 

 pressure in the glomerulus and for a lower and more constant 

 pressure in the second set of capillaries around the uriniferous 

 tubules. On account of the resistance offered by a double 

 system of capillaries the blood pressure in the kidneys is kept 

 relatively high. 



The changes in blood pressure may be observed upon the 



Fig. 1. 



1. Artery. 2. Glomerulus. 3. Capsule of Bowman. 4. Convoluted 

 portion of Tubule. 5. Capillary net work. 7. Loop of Henle. 8. Collect- 

 ing Tubule. 9. Opening of Tubule on Papilla. 



