504 EDWARD B, MEIGS 



METHODS OF EXPERIMENTATION 



It has been found convenient to put the protocols of the experi- 

 ments together at the end of the article. These protocols give, 

 for the most part, the results of experiments in which pieces of 

 frog's muscle were immersed in various solutions and weighed at 

 intervals. All the tissue came from three American species of 

 frogs^ — the bull-frog (Rana catesbiana), the leopard frog (Rana 

 pipiens), and the green frog (Rana clamitans). In most of the 

 experiments the changes of length undergone by the smooth mus- 

 cle were followed and the irritability of both the smooth and stri-. 

 ated muscle used was tested at intervals. The temperature is 

 also given with each experiment. In most cases this represents 

 the temperature of the room at a point near that at which the 

 experiment was carried out; it may be taken to be within a degree 

 of that of the solution in which the muscle was immersed. In a 

 few cases, where the effects of temperature were particularly to be 

 studied, the actual temperature of the fluid in which the muscle 

 was immersed is given. 



The protocols represent selected experiments, which have been 

 confirmed by a varying number of other unpublished experiments. 

 I have not thought it worth while to add to the already rather 

 formidable mass of material by publishing all the duplicate 

 experiments. Duplicate experiments have been published in a 

 few cases for the purpose of showing small variations in the behav- 

 ior of the tissues, or because the points illustrated were thought 

 to be particularly important. 



The solutions used were made with water distilled over glass and 

 with either Merck's or Kahlbaum's chemically pure compounds. 

 The lactose used in Experiments 78 and 79 was a Merck prepara- 

 tion recrystallized several times and experimentally determined 

 to be free from nitrogen and ash. It is difficult to get a pure lac- 

 tose preparation, and smooth muscle behaves very differently in 

 pure sugar solutions and in sugar solutions to which even very 

 small quantities of electrolytes have been added. The Ringer 

 solution used had the following formula: 



