BLOOD-VESSELS OF THE HEART VALVES 453 



dist^oh'ed, it was filtered 8e\eral times through d()ul)le thicknesses 

 of cheese-cloth. 



Carmin: (Griibler's preferred). Sufficient carmin to make 1.5 

 per cent solution when added to the gelatin solution was pul- 

 verized in a mortar, while enough water was added to make a 

 thick paste. The carmin was then dissolved in ammonium hy- 

 droxide of known strength. The ammoniacal solution of carmin 

 was then quickly poured into the warm solution of gelatin and 

 thoroughly stirred. To this mixture was added slightly less 

 than the calculated amount of acetic acid required to neutralize 

 the ammonium hydroxide. The color of the carmin-gelatin 

 should be dark red, almost like the color of venous blood. A 

 light red color indicates that too much acid is present, and the 

 carmin will be found in small granules when a drop of the fluid 

 is examined under the microscope. If the mass is slightly alka- 

 line, the dye will diffuse through the injected tissues. The final 

 adjustment of the reaction of the mixture was made from data 

 obtained by titrating small amounts of it against the solutions of 

 ammonium hydroxide and acetic acid. The sweetish odor of 

 the mixture when it is neutral, supplanting the acid or ammonia- 

 cal odor of the first stages of the preparation was found to be as 

 valuable as any other indicator of the optimum reaction of the 

 mixture. When neutral, the mixture was filtered through double 

 thicknesses of cheese cloth After the addition of a few crystals 

 of thymol, the carmin-gelatin was stored in flasks until needed. 

 To prepare this for use, it was melted on a water-bath, and kept 

 at 45°C. during the injection 



The preliminary experiments were performed upon the hearts 

 of pigs, one or two years old, obtained from the slaughter house. 

 The heart-valves and chordae tendineae of these animals are 

 supplied with \'essels which, in microscopic sections, are seen to 

 contain blood-cells. With this assurance that the heart-valves 

 of the pig contain blood-vessels experiments were begun with the 

 preconceived notion that it w^ould be a simple matter to inject 

 the vessels with carmin-gelatin. Many attempts were made 

 before the proper conditions were found, and forty-six hearts 

 were used before a satisfactory injection was obtained. The 



THE AMERICAN JOURNAL OF ANATOMY, VOL. 21, NO. 3 



