352 SCIENCE PROGRESS. 



the gut ; the cells only load from the gut, and discharge 

 into the body cavity. He further maintains such movements 

 are visible in the cells of the absorbing skin of the frog, 

 when the edge of the web is observed in profile. 



Heidenhain is doubtful of these observations, on account 

 of the ease with which passive changes in the shape of the 

 cells produced by contraction of the musculature of the gut 

 may be mistaken for those possibly of active origin. 



Whatever may be the final decision as to the mode of 

 production of "physiological'' secretory and absorptive 

 pressure, it must be admitted that the time has now arrived 

 when the latter must be as definitely accepted as has been 

 the case with the former for more than forty years. 



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