THE MECHANISM OF THE SECRETION OF URINE. 



By ERNEST H. STARLING. 



CONTENTS. Theories of Urinary Secretion, p. 639 Theory of Bowman, p. 639 

 Theory of Ludwig, p. 640 Secretion of Water, p. 641 Methods, p. 642 

 The Concentration of the Urine, p. 650 Heidenhairi's Criticism of the Theory 

 of Ludwig, p. 652 Experiments of Nussbaum, p. 655 Experiments of Ribbert, 

 p. 656 Experiments of Bradford, p. 656 The Influence of the Nervous 

 System on the Secretion of Urine, p. 659. 



THEORIES OF URINARY SECRETION. 



IN all the organs of the body whose functions have been investigated by 

 physiologists, it has been found that ;i difference of function is invariably 

 associated with a difference in structure, so that the interdependence 

 of function and structure has become an axiom. AYe are therefore 

 justified in founding theories concerning the physiological function of 

 an organ on a purely anatomical study of its structure, although the 

 Complete establishment of such theories must ultimately be afforded 



^ 



The kidney differs from all other secretory glands, in the fact that 

 at the blind end of its tubulus we find a structure the glomerulus 

 where the vascular capillaries abut directly on the lumen of the tubulus, % 

 without the interposition of any lymph space. Ever since the publication 

 of "Ho wi n an 's /ffiaffl i* rm_ t,h e Ma.] pi gl i i a/n bodies of the kidney, these have 

 been looked upon as the essential source of the watery constituents of 



Theory of Bowman. Bowman. 1 who founded his theory of urinary 

 formation exclusively on the anatomical structure of the kidnev in 

 jajipjisJanimals. concluded that "as the t.nhp.a fl-nf ''thpiv plexus of 



capillaries were proba >ly the parts concerned in the secretion of that, 

 portion of the urine to which its characteristic properties are due (the 

 invH. lithic acid, etc.), the Malpighian bodies might be an apparatus 

 jjestined to^se^arate i'rom the blood the watery portion." 



The following are the grounds on which Bowman based this 

 hypothesis : 



(a) That the tubes are secretory. 



(1) The extent of surface obtained by the involutions of the 



tubules. 



(2) The fact that the lining membrane of the tubules is formed 



by thick epithelial cells, similar to those found on the 

 secreting surface of all true glands. 



1 PM. Trans., London. 1842, p. 57. 



