The Preservation of Material. 287 



Finally, there are characteristic changes in the body. The abdo- 

 men 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, preferably for a few hours, but if wanted 

 for use immediately the injection' may be made after several 

 minutes, usually with satisfactory results. 



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 after- 

 wards a brighter appearance, 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 coagu- 

 lated 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 



