THE PRESERVATION OF MATERIAL 369 



completed should be about 7 cm. long; and its narrow end should 

 have a uniform diameter of 1.5-2 mm. for about 2 cm. at the tip. 

 A slanting tip, produced by careful grinding on an emery stone 

 aids insertion into the vessel. The tip should be touched lightly 

 in the flame in order to round the margin by fusion, otherwise it 

 might damage the wall of the vessel. 



The rubber tubing used to connect the cannula with the main 

 tube should be of the best quality of soft rubber, and should have 

 an inside diameter of 4 mm., i.e., of proper size to slip on and off 

 the cannula easily, but yet to retain its hold on the latter under 

 moderate pressure. 



The reservoir for holding the embalming fluid may be an 

 aspirator or irrigator bottle, an enamel fountain, percolator, or 

 ordinary funnel. It may have a capacity of one or two quarts. 

 The capacity, however, is immaterial, so long as the operator keeps 

 the fluid replaced. The reservoir is suspended in such a way that 

 it may be moved up and down within a distance of four feet above 

 the top of the operating table. 



When large numbers of animals have to be prepared, it is useful 

 to connect the reservoir by wide rubber tubing to a horizontal 

 brass pipe six feet long, which is provided with five jets with taps. 

 A short length of quarter-inch rubber tubing connects each jet to 

 a Y-tube of glass or brass, which is in turn connected by slightly 

 smaller tubing to two cannulae. Thus ten animals may be em- 

 balmed simultaneously. 



At the time of beginning the embalming process the operator 

 should have before him the reservoir, suspended at a height of 

 about three feet, and a column of fluid, free from air-bubbles or 

 foreign material to the tip of the cannula. This condition must 

 be maintained throughout the operation. If at any time the 

 pressure falls in the apparatus sufficiently to admit air, or allow 

 coagulated blood to run back through the cannula, there is almost 

 certain to be trouble, not only with the specimen under treatment, 

 but also others which come after. The column of fluid is held back 

 until the proper time by a clamps placed on the rubber tubing. 



The animal is killed by administering ether or illuminating gas. 

 It is placed on its back on the table, with the head away from the 

 operator. The skin is first divided by a small incision on the inner 



