740 FEED C. KOCH 



action or, unless the proper precautions have been taken, it might be a 

 secondary effect as a result of a primary gastric stimulation. 



Specific Chemical Nature of Gastrin. In view of various reports as 

 to the physiological action and distribution of gastrin, as discussed above, 

 the questions which may be asked as to chemical character of gastrin 

 are : first, are gastrin and secretin the same ; second, is there one and the 

 same substance, vasodilatin, in all these extracts and is it the substance 

 the physiological effects of which we are observing; third, is the active 

 substance cholin or histamin? 



If gastrin and secretin are the same they may possibly be protein 

 hydrolytic products which might be Popielski's vasodilatin. According 

 to the observations of Chizin (1914), purified peptone and proteose frac- 

 tions do not possess the secretagogue action, and Keeton, Luckhardt and 

 Koch (1920) found a carefully prepared pepsin digest of fibrin inactive, 

 although it must have contained all stages of hydrolysis from proteose to 

 amino-acids. Gastrin certainly is very much more stable than secretin. 

 Secretin is very readily destroyed by dilute acids, alkalies and oxygen, but 

 gastrin containing material can be boiled for hours in 20 per cent hydro- 

 chloric acid without any loss of activity and is extremely resistant in every 

 way. It appears to be a basic substance, in that it can be extracted from 

 alkaline aqueous solutions by amyl alcohol, and can then be recovered 

 from the latter by dilute acid solutions. Like histamin and probably like 

 secretin, it appears to contain the imidazol ring, it is precipitable by 

 mercuric chlorid, alkaline silver solutions and by phosphotungstic acid. 

 It differs from histamin, in that it is not precipitated by picric and pic- 

 rolonic acids. It is not identical with cholin as its chemical properties 

 show, and also, in that cholin has only a very slight secretagogue action. 

 If it is not the same as vasodilatin, can it be separated therefrom ? May- 

 dell claims that by means of alcohol and ether precipitation, one can 

 obtain a gastric secretin or gastrin free from the vasodilating ingredient. 

 Tomaszewski considers the active substance to differ from the vasodilatin 

 in Witte peptone, because he found, contrary to Popielski's claims, that 1 

 20 c.c. of a 5 per cent solution of the peptone when injected subcutaneously 

 caused no gastric secretion, but that when the same dose is injected after 

 adding thereto an active gastrin preparation a good physiological response 

 follows. Nevertheless, as stated previously, Tomaszewski appears to be- 

 lieve that the active substance is very widely distributed. It is interesting 

 to note that Eisenhardt (1910) finds the spinach secretin to behave chem- 

 ically in many respects the same as the gastric stimulatory substance, that 

 is, he finds it dialyzable, precipitated by phosphotungstic acid and by 

 silver in the arginin-histidin fraction. 



Mode of Action. Although not yet obtained in pure form, still we 

 have some light on this phase of the work. In the first place, the best 

 response follows an intramuscular or subcutaneous injection, only a slight 



