456 



PHYSIOLOGY 



CHAP. 



obliterated. The " brush-border/' however, is plainly visible, and 

 does not differ perceptibly in the two animals. The same may be 

 said of the nuclei which are found in the resting state in both 

 animals ; they are situated in the basal third of the cell ; and are 

 spherical, with an indistinct reticulum, and large nucleoli which 

 vary in number. On the other hand the cell-protoplasm shows 

 marked differences. In the waking marmot it consists of a series 

 of nodulated threads which radiate from the axis of the lumen 

 (and cause the striated appearance) ; they are more distinct and 

 regular in the basal half, more fused, nodulated and interwoven in 

 the inner half which faces the lumen. In hibernating marmots 



FIG. 123. (Left.) Section through convoluted tubule of marmot during advanced torpor. 



(R. and A. Monti.) 



FIG. 124. (Right.) Section of convoluted tubule of waking marmot, during functional activity 



of renal epithelia. (R. and A. Monti.) 



the protoplasm exhibits the same thready and striated composition, 

 but it is much less apparent, because it is masked by a large 

 number of irregularly distributed granules, which differ in size 

 and in their affinity for stains. They are not fat droplets, because 

 they do not disappear on prolonged immersion of the sections in 

 xylol or oil of bergamot. It is therefore probable that they consist 

 of protein, destined to maintain the secretory work of the cell, and 

 that they accumulate when the function of the kidneys is reduced to 

 the lowest terms, as must be the case after prolonged hibernation. 

 These results of the brothers Monti are still more important 

 from the physiological point of view. To us they appear to give 

 histological evidence of the active intervention of the cells of the 

 convoluted tubules in the functions of the kidneys, and therefore 

 prove the inadequacy of the purely mechanical theory to explain 



