The: Preservation of Material. 197 



of the body, and no clogging of the vessels need be feared. The fluid 

 may usually be observed running in the cannula, and, of course, falling 

 in the reservoir. Finally, there are characteristic changes in the body. 

 The abdomen becomes greatly distended, the subcutaneous tissue 

 swollen, the eyes protrude, and there is usually more or less frothing at 

 the nose. Leakage, either in the area of the incision or at the nose, is 

 sometimes a sign of too much pressure. In the former case the leakage 

 is frequently behind the cannula, and may be stopped by artery forceps. 

 In the latter case there is no recourse but to confine the fluid to the 

 nasal cavity by tying the nostrils. 



After the embalming process the rubber tube is disconnected from 

 the cannula, the latter being left carefully in place. The animal is then 

 set aside for twenty-four hours in an upright position. After this it is 

 ready for injection. 



The injection mass may be made by mixing ordinary starch and 

 water to the consistence of thin cream ; then adding a finely-ground 

 coloring material, such as vermilion or a very small quantity of carmine. 

 There is some advantage in using a 5% formalin instead of water alone 

 in making up this mass, the arteries having afterwards a brighter appear- 

 ance, which is doubtless due partly to better preservation and partly to 

 the fixing of the starch in the vessels. The mass must be thoroughly 

 strained before use, in order to avoid the presence in it of particles which 

 are too large to go through the cannula. The injection is made with 

 a syringe, the latter being provided with a rubber tube of the same kind 

 as that used in the embalming process. The mass is sent in by applying 

 a gentle, even pressure, and it is sometimes advantageous to allow the 

 injection to run backward and forward in the tube, each time applying 

 a little more pressure. When the vessels have been filled in this way, 

 the tube is clamped. By drawing on one cord of the ligature the knot 

 is loosened sufficiently to withdraw the cannula, and by keeping a 

 finger pressed on the end of the vessel, the knot may then be drawn 

 tight without loss of injection. 



It sometimes happens, despite ordinary precautions, that the cannula 

 becomes clogged either with settled starch or with coagulated blood. 

 In this case it may be easily removed, cleaned, and replaced. The same 

 cannula should always be used. 



Material prepared according to the directions given above will keep 

 indefinitely, provided, however, that precautions are taken to avoid con- 

 tamination from the surface. These are especially necessary in view of 

 the thick coating of hairs. It is a good plan, therefore, to sponge the 

 animal with a preserving fluid which will penetrate the coat imme- 

 diately, or if many specimens are being prepared, to immerse the whole 

 animal for a moment. A suitable fluid for this purpose is formalin- 

 alcohol, made by adding 2% of formalin to a mixture of equal parts of 

 ordinary spirit and water. The alcohol ensures immediate penetration 

 and assists the formalin in preservation. The fluid should be squeezed 

 out of the coat as much as possible. The presence of a considerable 

 quantity is not harmful, unless, after the dissection has begun, the fluid 

 should gain access to the tissues and destroy the effect of the glycerin 

 of the embalming fluid. 



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