CH. xxxvi.] EXTIRPATION OF THE KIDNEYS. 545 



protoplasm in the vegetable cell takes place, and if red corpuscles are used 

 they swell and liberate their pigment, fgntunic solutions produce neither of 

 these effects, because they have the same molecular concentration and 

 osmotic pressure as the material within the cell-wall. 



Extirpation of the Kidneys. 



Extirpation of one kidney for various diseases (stone, <fec.), is a 

 by no means uncommon operation. It is not followed by any 

 untoward result. The remaining kidney enlarges and does the 

 work previously shared between the two. 



Extirpation of both kidneys is fatal ; the urea, &c., accumulate 

 in the blood, and the animal dies in a condition of deep coma 

 preceded by convulsions (uraemia). See p. 552. 



Ligature of both renal arteries practically amounts to the same 

 thing as extirpation of the kidneys, and leads to the same result. 

 If the ligature is released the kidney once more sets to work, but 

 the urine secreted is then albuminous, owing to the epithelium 

 having been impaired by being deprived for a time of its normal 

 blood supply. 



Removal of one kidney, followed at a later period by removal 

 of a half or two-thirds of the other, leads in dogs, in which the 

 operation has been performed by Bradford, to a surprising result. 

 After the second operation the urine is increased in amount, and 

 the quantity of urea is much greater than normal. This comes 

 from a disintegration of the nitrogenous tissues ; the animal 

 wastes rapidly and dies in a few weeks. It is thus evident that 

 the kidneys play an important part in nitrogenous metabolism 

 apart from merely excreting waste substances. The exact 

 explanation has still to be found, but it is possible that the 

 kidney, like the pancreas and liver, and many ductless glands, 

 forms an internal secretion (see p. 493). 



The Passage of Urine into the Bladder. 



As each portion of urine is secreted it propels that which is 

 already in the uriniferous tubes onwards into the pelvis of the 

 kidney. Thence through the ureter the urine passes into the 

 bladder, into which its rate and mode of entrance has been 

 watched in cases of ectopia vesicce, i.e. of such fissures in the 

 anterior and lower part of the walls of the abdomen, and of the 

 front wall of the bladder, as expose to view its hinder wall 

 together with the orifices of the ureters. The urine does not 

 enter the bladder at any regular rate, nor is there a synchronism 

 in its movement through the two ureters. During fasting, two 

 or three drops enter the bladder every minute ; each drop as it 

 K.P. N N 



