84 



taken place, very thin free hand sHces are cut with a sharp razor 

 from different parts of the head, tail and body of the pancreas re- 

 spectively. Pieces from each of these sections are rapidly teased 

 on the slide in Einger's solution and left exposed to the air without 

 a cover glass while counting other slides. When a teased prepara- 

 tion appears a little too blue, it can be improved by placing on a 

 cover glass and setting aside while counting others. A certain amount 

 of reduction usually takes place in the covered preparation. For a 

 longer preservation of the contrast between islands and acini, small 



Fig. 1. Islands of Langerhans in a teased preparation from subject 7. Sixteen 

 islands of various sizes are shown in a single field of the microscope in sharp con- 

 trast to the acinous tissue. Intra vitam staining with janus green, X 78. 



pieces of pancreas may be teased in ammonium molybdate (5% so- 

 lution in water), instead of in Ringer's solution, if one is sure that the 

 preparation shows the proper amount of reduction. However, I have 

 found that ammonium molybdate soon clouds the preparation and 

 renders a blue one valueless It sometimes happens that the reduc- 

 tion has gone so far that a green stain in many of the islets no longer 

 obtains. Careful teasing and study in this case will still show some 



