PANCREAS OF THE PIG 211 



E. C. Hill COG) working in this lal)()ratory, first injected the 

 embryonic bile-ducts in pigs by filling the stomach with India 

 ink by a hypodermic syringe. He attempted the same experi- 

 ment with the pancreas, but merely reports "not \'ery fruitful 

 results." I have followed this hint and developed a successful 

 method. To inject smaller embryos, hollow glass needles are 

 used, which must be drawn from tubing, of such a sharpness that 

 they will easily pierce, without tearing, the paper-thin walls of 

 the stomach; at the same time the needles should taper quite 

 rapidly, so as to plug tightly the aperture made by them in the 

 stomach, and thus prevent regurgitation of the injection-fluid. 

 The operator holds in his mouth a rubber tube, reaching to his 

 hand; at the end of this tube the needle is inserted (Popoff's 

 method, '94). The needle is filled by suction with the fluid, 

 which is Higgins' waterproof ink, diluted. The embryos need 

 not be warm, but should be used within 2 to 3 hours after removal. 

 The left abdominal wall is slit open, the stomach exposed, and 

 the needle thrust into its lumen. The operator then blows forci- 

 bly until the ink has distended several coils of intestine. The 

 stomach acts as a pressure bag. and the ink usually backs up 

 into the pancreatic ducts without extravasation. The extent 

 of the injection cannot l)e controlled; it may I)e partial, complete 

 in the head of the pancreas, or ciuite complete. 



This method succeeds only in embryos from 30 to 70 mm. 

 long. Below 30 mm. the ink does not enter the pancreatic 

 duct, although it may easily V)e forced through the entire intes- 

 tinal canal. Above 70 mm. the diagonal course of the duct 

 through the intestinal wall acts as a valve to prevent influx of 

 the ink. In the larger embryos and foetuses, therefore, recourse 

 must be had to still finer methods in order to enter the 

 duct itself. I have had full success with the method used 

 in this laboratory for some years by several investigators in 

 the study of blood and lymphatic capillaries. Delicate hol- 

 low glass needles are drawn, of a diameter of 25 to 50 micra. The 

 intestinal viscera are removed from the embryo and very care- 

 fully dissected under the binocular microscope in water or salt 

 solution imtil only the stomach, duodenum, and pancreas re- 



