38 MACDOUGAL^ACTION OF LIPOIDS IN GROWTH. 



The importance of the entire matter is such that two series of 

 experiments were designed in my own laboratory, the resuhs of which 

 might have a bearing upon the above conckisions. In one the auxo- 

 graph was used to register variations in thickness indicative of 

 changes in turgidity of cell-masses subjected to neutral salts and other 

 solutions. Next lipoids were introduced into the construction of the 

 artificial cell recently designed, and the effect of such substances 

 upon permeability of plasmatic layers of cell colloids under the in- 

 fluence of salts, saponin, and soaps was determined. 



Brief mention has already been made of the artificial cell used.^ 

 The cell in question was of a design in which clay, porcelain, alun- 

 dum, or wooden thimbles representing various degrees of porosity 

 were used to represent the external wall, while the plasmatic layer 

 could be represented by a plasmatic lining layer of any jelly or mix- 

 ture of jellies. The thimbles were fitted with an osmometer head 

 consisting of a stopper pierced with two holes, in one of which was 

 fitted a filling funnel with stopcock, and the other with an outlet tube 

 bent to the horizontal immediately above the stopper. Such an 

 arrangement permitted the measurement of endosmosis by the amount 

 of liquid forced out and caught in a small graduated receiver. The 

 greater number of experiments were made with the clay thimbles used 

 in the Livingston evaporimeter (Fig. i). Cells of this type lined 

 with agar treated with tanning reagents and fitted with vertical outlets 

 to show pressure, designed by Professor H. M. Richards, have been 

 in use for some time in the Botanical Laboratories of Barnard College. 

 As arranged in the work described here, the pressures in the cell 

 were never more than that of 12 or 15 mm. of water. 



The arrangement of this artificial cell was begun by washing the 

 thimbles in warm distilled water and preparing a liquid mixture of 

 the materials for the plasmatic lining layer. About 10-12 cc. of this 

 material was poured into the warm, moist thimble at a temperature 

 of 40-50° C, the osmometer head put in place, and the thimble turned 

 in the hand in a horizontal position. If a coating of 2 or 3 mm. in 



8 MacDougal, D. T., " The Distentive Agencies in the Growth of the 

 Cell," Proc. Soc. Exper. Biol, and Med., 19: 103-110, 1921. See original de- 

 scription of this cell in the Report of the Dept. of Bot. Res., Carnegie Inst. 

 Wash, for 1921. 



