482 PROCEEDINGS OF THE AMERICAN ACADEMY, 



nally obtained their salts from the medium. It is assumed here that 

 although some of the salts contained in the cell may possibly be in a state 

 of chemical combination with proteid, yet a considerable proportion of 

 them exist in a condition to produce osmotic phenomena. They are 

 either free and in simple solution (in vacuoles, Biitschli), or at most in 

 fsuch unstable combination, physical or chemical, as to be easily broken 

 down into more numerous portions, tliereby becoming osmotically more 

 active. 



When, therefore, Stentors are transferred from a normal medium to 

 very pure distilled water, there results the osmotic relation of a salt 

 pressure within the Stentor cell that is higher than that existing in the 

 distilled water externally adjacent to it. What process ensues under 

 these conditions depends, at least in large part, upon the degree of per- 

 meability of the protoplasm, including the walls of the protoplasmic 

 alveoli (Biitschli) as well as the cell-walls. If the cell-wall of Sten- 

 tor had been wholly impermeable to salts, much water would have been 

 absorbed (assuming of course free permeability for water), no increase 

 of salts would have taken place in the distilled water, and the animals 

 would have died of swelling ; but neither of these plienomena was ex- 

 hibited. On the contrary, the evidence that there is an increased salt-con- 

 tent in the distilled water demonstrates the greater or less permeability of 

 Stentor to physiological salts when the animal is surrounded by distilled 

 water. But I will note in passing that I do not conceive the permea- 

 bility of Stentor when in very pure distilled water to be the same as 

 when the cell is surrounded by the normal conditions of partial pressures 

 of salts. I have been led to this opinion by the results with milk sugar, 

 as I shall presently explain. We are now able to assign loss of salts as 

 the chief factor in the destruction produced by distilled icater, possibly 

 brought about, as implied above, by an abnormal condition of the cell- 

 wall induced by contact with water free from salts. The more permeable 

 the cell-wall, the more rapid would be the loss of salts, and the less, con- 

 sequently, would be the absorption of water. Careful observation failed 

 to show any evidence of swelling due to an increased water-content, 

 which, however, probably took place to some extent. Evidently the loss 

 of a portion of its salts has much more serious consequences for the 

 animal and its metabolism than some increase in its water-content. I 

 must here emphasize, for the i)urpose of a subsequent comparison (p. 500), 

 the fact that cdl the permeating salts share in this process of withdrawal. 



The phenomenon of shrivelling, observable when molecular or hyper- 

 molecular concentrations of either physiological salts, or of practically 



