(LLOYD] PROPERTIES OF PROTOPLASM 137 



tion with gelatine with the purpose of determining not merely the 

 total swelling capacity, but the swelling rates. Growth is the resultant 

 of a complex of causes, of which the imbibition rate of protoplasm can 

 readily be conceived to be one, while it is equally thinkable that the 

 total imbibition capacity may not be made use of. The experiments, 

 which have been carried on during the past two years in this labor- 

 atory,^ consisted in measuring the increase in a linear dimension 

 (length) of strips of gelatine placed in the various media arranged in 

 series of concentrations, including pure water. The strips were 1 cm. 

 wide, 5 cm. long, and 0-2 to 0-4 mm. thick. Gold Label French 

 gelatine was used. The fluid and gelatine were placed in a large 

 Petri dish and measured with a thin scale lying beneath. The 

 amount of swelling was expressed as percentage on the original 

 length- at the close of short intervals, thus, taken seriatim, affording 

 an expression of swelling rate. 



The effect of acids. Hydrochloric, nitric, sulphuric, citric, malic, 

 tartaric and acetic have been studied. In general it was found that 

 for all acids there is a concentration (about N/320, sulphuric acid) 

 which induces the maximum rate of swelling, and a concentration 

 which represses swelling (about N/2800, sulphuric acid) to a rate lower 

 than that in pure water. The rate of swelling is greater at first in 

 higher concentrations (N/20, sulphuric acid), but is gradually over- 

 taken by lower concentrations until that of N/320 is reached. The 

 total swelling remains, after 15 hours, greatest in N/320> N/20> 

 water> N/1280, which accords with earlier findings. 



The maximum swelling rates in organic acids occur at higher con- 

 centrations, e.g. in formic citric, tartaric acid at N/40; acetic at about 

 N/10, malic N/10. 



The repressing effect of acids at low concentrations was shown 

 especially well by acetic acid, the minimum rates occurring at N/640 

 to N/2560, and giving, after 20 hours, a total swelling of about 15% 

 less than in pure water. When combined in the ratio 1 :1 with sodium 

 acetate, the maximum rates are reduced to about one third at the 

 higher concentrations (N/20) and one half at N/160, while the minimum 

 rates are slightly depressed but obtain over a wider range of con- 

 centrations (N/320 to N/2560). Analogous results were obtained 

 with potassium nitrate and nitric acid. 



The effect of salts. Salts alone repress the swelling of gelatine in 

 general below that in water. The effect is however not in a regular 



'The writer wishes to acknowledge the assistance of Miss Mary E. Ciirrie, Mr. 



J. S. Murray, Mr. George Hanson, and Mr. F. VV. Stavely in prosecuting this work. 



-It should be noted that gelatine swells most in the direction of its least dimension. 



Sec. IV, Sig. 10 



