76 



Dr. J. Homans. The Relation of the [Oct. 1, 



of sectioning. Sections cut less than 4 micra in thickness were stained by the acid- 

 fuchsin-methyl-green method advocated and fully described by Bensley. 

 II. Aqueous-chrome-sublimate (Lane's method for B cells). 



Very small pieces of tissue were fixed for 12-24 hours, washed in water and passed 

 through alcohol (including an iodine solution) to paraffin. These sections were stained 

 for 24 hours in a 20-per-cent. solution of neutral gentian. (For the details of preparing 

 this solution see Lane's or Bensley's article.) 



III. Alcohol-chrome-sublimate (Lane's method for A cells). 



Tissues fixed in this solution for thi-ee to four hours with one change were washed in 

 50-per-cent. alcohol and passed rapidly through alcohols to paraffin. Neutral gentian 

 stain. 



(As this method produces considerable shrinkage, and as in my hands it has proved 

 quite uncertain, especially in the dog, I have made little use of it.) 

 IV. Zenker's fluid. 



Tissues treated were stained with methylene blue and eosin or a similar combination. 

 This technique does away with the granules in the acini and islets as well, and may be 

 used to show the " negative " of the granule stains. 



Demonstration of Islets by Vital Staining Methods. — I have repeated a number of 

 Bensley's experiments to satisfy myself that they are valuable in less skilled hands than 

 his. Only the neutral red, pyronin and methylene blue methods have been used. 

 A full description will be found in Bensley's article. 



1. Partial Removal of the Pancreas. — Under morphine and ether the pancreas, with 

 the exception of about one-tenth at the duodenal end, was removed by blunt dissection 

 (Hedon's method) without ligation of blood vessels. There was no bleeding. The cut 

 end of the remaining part, generally about 2 cm. in length, was tied off with silk and 

 was either transplanted with its blood supply outside the oblique muscles through a slit 

 in the muscle or left in situ. 



2. Ligation of the Ducts. — Under morphine and ether the large duct was isolated for 

 \ cm. and divided between two silk ligatures. The pancreas in this region was separated 

 from the duodenum, and omentum was inserted between the gland and the bowel. To 

 divide the smaller duct the tissues about the common bile duct were ligated on both 

 sides and divided. The gland was further separated from the bowel and omentum 

 inserted between. 



3. Exhaustion of the Dog's Pancreas by Secretin. — The animals were fed as usual the 

 afternoon before the experiment. They were anaesthetised by morphine and ether. 

 A secretin solution prepared from small intestines by the method of Bayliss and 

 Starling was allowed to run into the external jugular vein by means of a cannula. 

 A cannula was tied into the pancreatic duct and the juice measured. A piece of 

 pancreas was isolated at the beginning of the experiment as a control of the exhaustion. 

 The stimulation was kept up until the pancreas failed to respond to the stimulation or 

 until the dog died. 



Potassium bichromate 



Mercuric chloride 



Distilled water 



2 - 5 grin. 

 5 „ 

 100 c.c. 



Saturated alcoholic solution of mercuric chloride. 

 Potassium bichromate, 2 '5 per cent. 



(Equal parts.) 



Operative Procedure. 



