aSS FROM FISH TO PHILOSOPHER 



The effective agent reducing the glomerular circula- 

 tion in the frog appears to be the oxytocic fraction, but 

 in the toad, aUigator, and chicken, the effective agent is 

 ADH. With respect to reduction in glomerular activity, 

 the toad, v^hich is better adapted to terrestrial conditions 

 than is the frog, is much more sensitive to neinrohypo- 

 physial extracts than is the latter animal, indicating that 

 pituitary control of the glomeruli is subject to quanti- 

 tative variation even among the Amphibia {96}. 



In the mammals the oxytocic fraction probably par- 

 ticipates in parturition by stimulation of the uterus, and 

 in lactation; what function it may have had in the ostra- 

 coderms and fishes lies beyond conjecture. 



Whether a pituitary hormone is involved in the con- 

 trol of the glomerular circulation in the fishes, and 

 notably in marine forms where glomerular activity is 

 markedly reduced (Chapter VIII) , is undetermined. 



Intermittent glomerular activity, involving some or 

 even all the glomerular capillaries, was described many 

 years ago in the frog's kidney by A. N. Richards and 

 C. F. Schmidt, but A. L. Grafflin and E. H. Bagley {89} 

 have recently adduced evidence that this phenomenon 

 is attributable to the abnormal state of the experimental 

 animals, and that spontaneous intermittence is probably 

 not a characteristic feature of the glomerular circulation 

 under normal conditions. This conclusion, however, does 

 not detract from the significance of reduction in glo- 

 merular filtration (by alternation of activity or otherwise) 

 during dehydration {86, 87}. The problem is. When 

 is a frog in a normal state of hydration— when submerged 

 to the nose in water, or when sitting on a shaded lily pad? 



The absorption of sodium chloride by the skin in the 

 Amphibia has been extensively studied by Krogh {65} 

 whose work is summarized by Prosser et al. {54} » by J0r- 

 gensen {90}, and most extensively by Ussing and his 

 collaborators {98a}. 



