174 



Scientific Proceedings (39). 



The response of a muscle to chloroform or saponin after 

 treatment with a strongly sensitizing solution, as w/8 NaI,ra/8 

 NaC10 3 , m/S NaN0 3 , or m/8 NaCNS, approaches closely in char- 

 acter to the normal contraction, i. e., the upstroke is rapid and 

 accompanied by often vigorous twitching. There is, however, no 

 relaxation; and the associated coagulative change in the tissue- 

 colloids is more pronounced than in the unsensitized muscle simi- 

 larly treated. In other words, there is a correlation between the vigor 

 of the contraction and the degree of the coagulation, indicating that 

 the fundamental change in contraction is of the same nature as in 

 colloid coagulation, i. e., that contraction is the expression of a 

 coalescence of colloidal particles in the fibrillae, due presumably to 

 increased surface-tension of these particles. These experiments 

 also indicate that rigor contraction is of the same essential nature 

 as normal contraction. 



in (521) 



A new method for the analysis of proteins. 



By DONALD D. VAN SLYKE. 



[From the Laboratories of the Rockefeller Institute for Medical 



Research.) 



The method outlined will serve to supplement the ester method, 

 and to characterize proteins when relatively small amounts of 

 material are available. Two and a half grams of protein are hy- 

 drolyzed by 15 to 18 hours boiling with 20 per cent, hydrochloric 

 acid. The solution is concentrated to a syrup, then transferred to 

 a one-liter Claissen distilling flask with 200 cubic centimeters of 

 water. Saturated barium hydrate solution to 25 cubic centimeters 

 excess is added and the ammonia is distilled in vacuo into N/io 

 sulphuric acid from a bath at 45 0 C. The residual solution is 

 acidified with sulphuric acid and boiled while silver sulphate is 

 added until all the hydrochloric acid is precipitated. The pre- 

 cipitate, which carries the melanine with it, is Kjeldahled to deter- 

 mine the melanine nitrogen. The filtrate is brought to 100 cubic 

 centimeters and 5 cubic centimeter duplicates taken for total and 

 amino nitrogen determinations. 1 



1 Method for Determination of Amino Nitrogen, Proc. of the Soc. for Exper. Biol, 

 and Med., 1909, vii, 46. 



