vin THE EXCRETION OF URINE 443 



function of the gloineruli, as claimed by the Bowman-Heidenhain 

 theory. 



Some experimenters have made use of poisons, which attack 

 the separate parts of the kidneys electively, e.g. arsenic, aloiu, 

 chromic acid (Hellin and Spiro, 1897), or of circumscribed patho- 

 Inyical lesions, with the object of establishing a functional dis- 

 tinction between the elements of the kidneys. The able work 

 of Galeotti (1902) deserves special mention. He injected solutions 

 of 10 per cent sodium chloride or 130 per cent glucose solution into 

 the crural vein of dogs ; and then at different intervals took small 

 samples of blood from the carotid, and of urine from a catheter 

 tixed in the bladder. He determined the freezing-point and 

 electrical conductivity of both fluids, also for the urine the content 

 of organic and inorganic constituents, so as to obtain an approximate 

 notion of the work of the kidney. This w T ork was carried out 

 partly on normal animals, partly on animals that had been 

 poisoned with corrosive sublimate (w r hich particularly attacks the 

 uriniferous tubules), or cantharidiue (which specially affects the 

 glorneruli). His fundamental results are, briefly, as follows : 



() The increase of osmotic pressure in the blood produced by 

 injection of hypertonic salt or sugar solutions excites the kidneys, 

 by a mechanism of which little is known, to increased activity, in 

 order to bring the osmotic pressure of the blood back to its normal 

 value. This tendency can be detected even in kidneys which are 

 so profoundly altered that they fail to attain their object. The 

 elimination of salt or sugar is begun, according to the principle of 

 least labour, by a marked excretion of water, which makes it 

 possible to secrete many molecules of salt or sugar without raising 

 the osmotic pressure of the urine much above that of the blood. 

 If the dog is prevented from drinking, the excessive output of 

 urine ceases, because the need of the animal to retain water is 

 opposed to the tendency of the kidney to eliminate it. Under 

 these circumstances a concentrated urine must be passed, in order to 

 eliminate the abnormal constituents of the blood. The secretion 

 of this urine occurs, however, with a much higher expenditure 

 of work on the part of the renal epithelial cells, and may 

 involve their exhaustion and degeneration. 



(&) In the case in which, with unaltered function of the 

 glouieruli, the function of the epithelial cells is almost entirely 

 lost (corrosive sublimate poisoning), a copious urine of low 

 concentration is secreted; vice versa, when the gloineruli are 

 damaged and the epithelia intact (cantharidine poisoning), a 

 scanty urine of higher concentration than the blood is formed. 

 Hence there is a certain independence in the function of the 

 glomeruli and the tubules, seeing that injury to either induces 

 different functional alterations. 



(c) During filtration through the glomeruli the fluids on both 



