OBSERVATIONS ON A NEW TYPE OF ARTIFICIAL ^^^ 



OSMOTIC CELL .■ 'i. .^a^o 



» .^ I L I B ^ A " 



JOSHUA ROSETT \.-..-\ 



Baltimore, Maryland ' \r^» 



INTRODUCTION 



Students in plant physiology are familiar with what is called 

 Traube's' artificial cell — one of the means by which osmotic 

 pressure and some of the properties of precipitation membranes 

 are frequently demonstrated to elementary classes. It will 

 be remembered that these cells are formed by placing a frag- 

 ment of CUSO4 in a weak solution of K4Fe(CN)6, that a brown 

 membrane of copper ferrocyanide is instantly formed about the 

 mass, and that the cell thus formed enlarges for a considerable 

 time, this enlargement being due to repeated osmotic ruptures 

 of the membrane and subsequent closings of these openings by 

 new precipitation. 



The writer has been interested in the osmotic and chemical 

 phenomena involved in this sort of ''osmotic growth," and 

 has been able to improve the technique so as to bring out several 

 new details of the processes involved. Some of the results 

 should be of interest to physiologists as furnishing examples of 

 certain physico-chemical and colloid-chemical phenomena that 

 may need to be considered in connection with the analysis of 

 the growth processes of living cells. Aside from serving as 

 simple illustrations of certain general phenomena that are ap- 

 parently very roughly paralleled in the tissues of organisms, 

 these artificial growths also furnish opportunity for the deeper 

 study of the phenomena themselves. But it must always be 

 borne in mind, in such studies, that the processes of enlargement 



^ Pfeffer, W., Physiology of plants, translated by A. J. Ewart, vol. 1, p. 106. 

 Oxford. 1900. For the original work on precipitation membranes, see: Traube, 

 M., Experimente zur Theorie der Zellenbildung und Endosmose. Arch. Anat. 

 Physiol. 1867: 87-165. 1867. 



37 



THE PLANT WORLD, VOL. 20, NO. 2 

 [•EBRUARV, 1917 



