83 



In each case to get a good injection was the principal object. However, 

 the first two trials showed me that it is very easy to overstain the 

 human pancreas, thus rendering a reliable count impossible. The 

 dilutions which so far have given the best results are 1 to 50,000 for 

 neutral red and 1 : 30,000 for janus green. Solutions stronger than 

 these are likely to overstain. With those of a greater dilution the 

 pancreas shows a tendency to become edematous, which interferes 

 with the free flow of the injection fluid before a proper stain is attain- 

 ed. When a good grade of janus green was obtained the neutral red 

 method was dispensed with, since a sharper contrast and more reliable 

 results were obtained with janus green. Ringer's solution was also 

 substituted for 0,9% sodium chloride solution. The procedure, to 

 some extent influenced by local conditions, is as follows: having 

 previously ligated all the arteries of the abdomen except those which 

 supply the pancreas, including also two ligatures around the aorta 

 (one just above the diaphragm, the other about the place of origin 

 of the spermatic), the pancreas was thoroughly washed out with 

 two or three liters of Ringer's solution, using a low pressure at first. 

 The injecting pressure should never go much above the normal blood 

 pressure while the pancreas is being washed free from blood. The 

 pancreas, duodenum and spleen with all surrounding tissue were 

 then cut out and taken to the laboratory for injection. Janus green- 

 in Ringer's solution, 1 : 30,000, was injected into the pancreatico- 

 duodenal and splenic arteries till the pancreas was of a deep green 

 ish blue tint. This requires from 2 to 5 liters of injection fluid. The 

 pressure was gradually raised to double the normal blood pressure 

 or higher during the passage of the last liter of injection fluid. The 

 pancreas was then covered up Avith a piece of mesentery and allowed 

 to stand till it became a deep rose-pink, and until a sample taken 

 from time to time showed the islets standing out as deep green dis- 

 creet bodies on a pink background of acinous tissue. This requires only 

 a few minutes and care must be taken that reduction in the deeper 

 parts does not go too far, since, as Bensley has pointed out, once 

 the green color of the islets is lost by reduction, exposure to the air 

 does not bring it back, as is the case (to a greater or less extent) with 

 neutral red. This is especially true of the head which shows a great 

 tendency to rapid reduction (due, no doubt, to its greater thickness 

 and its being well covered up b}' the duodenum). 



When a trial has shown the proper amount of reduction to have 



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