32 Drs. J. Lewkowitsch and J. J. E. Macleod. [May 11, 



placed into a second test tube, the pancreatic extract having, in this 

 case been heated to destroy its ferments. The preparations were 

 incubated at 37 C. After about half-an-hour the preparations were 

 examined In the case of the steatolytically active mixture, the 

 contents of the test tube were found to be discolounsed, and 

 amount of decinormal caustic soda solution necessary to restore the 

 original red tint was ascertained. Preparations C and D were obtained 

 from 200 grams minced, fresh pig pancreas by simply triturating in a 

 mortar with twice the bulk of water. In these cases the preparations 

 were not incubated, for it was evident that in the previous experiments 

 with A and B the steapsin had been destroyed, as the preparations, before 

 incubation, were very active steatolytically when tested by the above 

 method, but only very slightly so after incubation ; probably this was 

 due to the action of trypsin on steapsin. It was also noticed in 

 preparations A and B that the steapsin remained on the filter paper 

 when the solutions were filtered, the filtrates having much weaker 

 steatolytic powers than the precipitates. Preparations C and D were, 

 .therefore, only filtered through muslin. 



Preparation of the Emulsion of Fat and Steapsin. 



100 grams of cotton-seed oil, or lard, were weighed out and care- 

 fully triturated in a mortar with measured quantities of the pancreatic 

 extract. Great care was taken to obtain a complete emulsion. The 

 emulsion was then poured into bottles which were well corked to 

 exclude growth of fungi, and allowed to stand at the ordinary 

 temperature.* If the temperature was raised too rapidly, say by 

 immersion in a water bath kept at 30 or 35 C, the emulsified mass 

 would separate into two layers, and no hydrolysis would then take 

 place. It is therefore of the greatest importance to carefully observe 

 the mixture for some hours, and to thoroughly shake them up as soon 

 as signs of separation are noticed, in order to restore the state of 

 emulsion. A good plan is to immerse the well-shaken emulsion 

 in cold water, or to let it stand in the open during the night. 

 After a few days, distinct hydrolysis is noticeable. In the case of 

 cotton-seed oil, the outward sign of hydrolysis is the hardening of the 

 mass, due to the fatty acids that have been formed. 



Consideration of Results. 



The following table contains a series of observations made on cotton- 

 seed oil and lard. The amount of hydrolysis was measured by the 

 percentage of free fatty acids, expressed in terms of oleic acid. The 



* Most of the preparations kept free from infection during the time these 

 experiments lasted. Only a few became covered with growth of Penicilliwn 

 glaucum after the lapse of about four weeks. 



