272 APPLIED PHYSIOLOGY 



glomeruli are capable of some selective action. The 

 proteins of the blood, for instance, are not excreted by a 

 healthy kidney, whilst ' foreign ' proteins, such as egg 

 albumin and peptone, are. Good examples of such 

 selective excretion of foreign proteins are also seen in 

 human pathology in the excretion of haemoglobin by the 

 kidney in paroxysmal haemoglobinuria, and of the so- 

 called ' Bence Jones's albumose ' in myelopathic albu- 

 mosuria, and a study of the urine in these diseases is 

 alone sufficient to disprove any purely mechanical nitra- 

 tion theory of urine production. 



It cannot be said, however, that the clinician is acutely 

 interested in the physiological theories of renal function, 

 for when disease affects the kidney the organ usually 

 suffers as a whole, and it is but rarely that the glomeruli 

 or the tubules are either solely, or even preponderatingly, 

 involved. In scarlatinal nephritis, it is true, the glom- 

 eruli are sometimes much more disorganized than the 

 tubules, and such cases are characterized by the produc- 

 tion of a scanty and concentrated urine, which is evidence, 

 so far as it goes, in favour of the view that the glomeruli 

 are chiefly concerned in the production of water. It is 

 interesting to note that the epithelium which covers the 

 glomerulus is more differentiated than that which lines 

 Bowman's capsule, and, in harmony with this, it shows 

 a different reaction in disease. Like all highly differ- 

 entiated epithelia, it is very vulnerable, and its cells 

 readily necrose, a process which can be well observed in 

 a kidney which has been damaged by the excretion of 

 the poisons of scarlatina or diphtheria. The epithelium 

 which lines Bowman's capsule, on the other hand, par- 



