242 B. C. H. HARVEY AND R. R. BENSLEY. 



Cyanamin, according to Witt, possesses two basic groups, one 

 molecule of the base combining with two molecules of hydro- 

 chloric acid to form a bichloride which is soluble in water with a 

 deep blue color. On dilution of this solution the compound is 

 broken up into a monochloride insoluble in water, which deposits 

 as a reddish violet precipitate, and hydrochloric acid, which 

 remains in solution. On the addition of alkalies the solution 

 changes to a red color and after a short time the base settles out 

 as a red flocculent precipitate. 



On account of the formation of a monochloride intermediate 

 in color between the red base and the blue bichloride it is appar- 

 ent that as an indicator of reaction cyanamin does not approach in 

 delicacy of response the more commonly used chemical indicators. 

 But when we consider the relatively high content of hydrochloric 

 acid in the gastric juice (as high as .5822 per cent, according 

 to Rosemann ('07)) this is of little importance, for we have 

 found that in dilute solutions of the dye a concentration of .0009 

 per cent, of hydrochloric acicl, or approximately 1/600 of the 

 concentration in the gastric juice, is sufficient to abolish all trace 

 of red color. Furthermore, if Pawlow's idea is true that the 

 native secretion has a constant acidity, and that the variations in 

 acidity of the secretion from a gastric fistula are due to different 

 degrees of neutralisation by the alkaline mucous secretion of 

 the surface epithelium, then we might expect a maximum acidity 

 in the gland lumen assuming that the hydrochloric acid is secreted 

 as such by the cells. It follows therefore that if cyanamin stains 

 the gastric secretion in the glands it will stain it blue wherever 

 the acid is produced. 



The method of applying the cyanamin is as follows: A fresh 

 concentrated solution of the bichloride in normal sodium chloride 

 solution is prepared; the animal is killed by a blow on the head, 

 or by bleeding from the carotid, and the stomach exposed as 

 rapidly as possible; a small piece of the mucous membrane is 

 cut out with scissors, rinsed in normal salt solution, and placed 

 in the solution of the dye. A few minutes' immersion suffices 

 to accomplish the staining. When this is complete the piece 

 of mucout membrane is placed on a slide with the mucous surface 

 downwards and observed with a low power of the microscope. 



