454 STANHOPE BAYNE-JONES 



important considerations were the iiost-niortcni riji;or of the 

 niyoearchuni, the jirescMiee of ch)ts of blood or bubijles of air in the 

 small branches of the coronai-y arteries, the blocking of the large 

 blood channels so that the injected fluid would pass into the 

 valves, and the pressure required to force the gelatin into the 

 small lateral vessels of the annular arteries. When these factors 

 were properly arranged, the blood-vessels of the heart valves 

 of the pig could be injected with regularity. 



After these experiments, the procedure was as follows: The 

 heart was used immediately, if obtained within an hour of the 

 death of the animal. If not, it was kept in isotonic salt solution 

 at room temperature for 24 hours, until the rigor of the muscle 

 became soft and the vessels relaxed. The chambers of the 

 heart w^ere washed as free from clot as possible by allowing 

 water to flow through the auricles. The coronary sinus was 

 plugged wdth cotton and tied off gently. The cut edges of the 

 auricles were then closed with a purse-string suture, and the 

 pulmonary artery was tied off as high above the valves as pos- 

 sible. Small glass cannulae were then passed down the stump 

 of the aorta, into the orifices of the right and left coronary ar- 

 teries, and tied in place by a silk suture passed with a fine needle 

 around these arteries near the aorta. Care was exercised then to 

 close all open vessels and to cause no new ' leaks' from tissue torn 

 by the sutures. It was found to be of great importance to block 

 these wider channels, so that the injection mass could be forced 

 into the narrower course of the heart-valves. By an arrange- 

 ment w^ith an air-pressure apparatus, connected with a man- 

 ometer, the melted carmin-gelatin at a constant temperature of 

 45°C. was pushed into the coronary vessels under a pressure of 

 140 to 190 mm, Hg. while the heart w^as kept in a bath of 

 salt solution at 50°C. This high pressure appeared to be the 

 most important factor in the procedure Injection at the ex- 

 pected coronary blood-pressure of 110 to 120 mm. Hg. did not 

 penetrate into the valves. When, however, the higher pressure 

 was applied, many more small vessels became filled. The in- 

 jection was held at this stage for half an hour. At the end of 

 this time, while the pressure was maintained at 190 nun. Hg., 



