116 



pressing the basal metabolic rate by about one-half. A dose of 8.5 

 mg had roughly the same effect as a dose 16 times bigger, suggest- 

 ing that within this range the drug suppresses a process necessary 

 for the maintenance of the normal metabolic level but not indis- 

 pensable for life. Increasing the dose further killed the animals, 

 suggesting that at higher concentrations the drug attacked another 

 more vitally important process. Below 8.5 mg per kilogram the 

 action began to fade out altogether. Calculating the molar over-all 

 concentration (taking 1.2 g body weight equal to 1 ml) : 0.0013 

 M killed the animal, 0.00073-0.000044 M had roughly the same 

 strong effect, while the action began to fade out around 0.00002 

 M. As the table shows, the temperature of the animals dropped 

 during the experiment and so the drop in basal metabolic rate 



being too large and passing too rapidly through the liquid. This difficulty 

 was overcome by adding 5% butyl alcohol to the baryta, which makes the 

 bubbles smaller and makes them rise to the surface much slower. The whole 

 apparatus consisted of six units, making it possible to measure the CO2 pro- 

 duction of six mice simultaneously. Its essentials are shown in Fig. 12, in 

 which only one of the six units is represented. 



The experiment was performed as follows: 200 ml of 5% watery «-buta- 

 nol solution were placed into the glass cylinder (T), about 60 cm long and 

 6 cm wide, closed on both ends by rubber stoppers; 10 ml of 0.2 M baryta 

 were pipetted into the container B with a few drops of a 10% alcoholic 

 solution of the indicator. Then the animal was enclosed in a small cylindrical 

 wire cage, weighed, and placed with its cage into the short glass tube C, 

 closed on both ends by rubber stoppers. Air was sucked through this con- 

 tainer, liberated of its CO: in a soda lime tower (SL). The air was led from 

 C through a rubber tube and through the stainless steel filter disk F (A. H. 

 Thomas, Philadelphia, Catalogue No. 5151 S). This filter disk was mounted 

 into the lower rubber stopper in such a way that air could pass it only 

 through its upper surface. The air was sucked out of the cylinder T with a 

 constant negative pressure of 20 cm Hg. 



The air, passing through the filter, formed a fine foam which filled tube T 

 to about its middle. The rate of airflow was regulated by the clamp-screw R. 

 After everything was set, the baryta was allowed to run into T, the container 

 B rinsed. The measurement began with the running in of the baryta and 

 ended with the complete discoloration of the solution, the interval being 

 measured by means of a stopwatch. 



