[banting, etc.] preparation OF INSULIN 29 



layer saturated with salt and a lowermost layer consisting of crystals 

 of salt. The alcohol layer was removed by means of a pipette and 

 was at once delivered into several volumes of 95 per cent, alcohol, or 

 better, of absolute alcohol. It was found that this final treatment 

 with alcohol of high grade caused the precipitation of the active 

 principle along with adherent substances. Some hours after this 

 final precipitation the precipitate was caught on a Buchner funnel, 

 dissolved in distilled water and then concentrated to the desired 

 degree by use of the vacuum still. It was then passed through a 

 Berkfeld filter, sterility tests made and the final product delivered 

 to the clinic. 



The essential points relating to the extract prepared as outlined 

 above are: 



(1) It contains only a minimum of protein. 



(2) It is practically salt free and can readily be made isotonic. 



(3) It is lipoid free. 



(4) It is almost free from alcohol soluble constituents. 



(5) It can be administered subcutaneously without fear of any 

 local reaction. 



