INJECTION. 



[ 352 ] 



INJECTION. 



by a curved needle, the eye of which 

 carries the thread. As soon as the pipe 

 has heen fixed in the vessel, all other vessels 

 communicating with it should be tied around 

 with silk-thread or closed in some other way 

 that the injection may not escape; some- 

 times it is requisite to enclose a part of the 

 tissue itself in the ligature; in other instances 

 their closure may be effected by fusion of 

 the tissue at the spot from which the injec- 

 tion might escape by the application of a 

 red-hot iron. 



The organ or part to be injected is then im- 

 mersed in warm water, in order that it may 

 become heated throughout; and if it be 

 large and of considerable thickness, this may 

 take some time, and fresh warm water must 

 be added at intervals to keep it at the same 

 temperature, which should be about as great 

 as can be borne by the hand. If the water 

 be too hot, the vessels and tissues will 

 be rendered brittle, and the whole will be 

 spoiled. Moreover, the part should not be 

 kept longer in the water than is absolutely 

 requisite, for the same reason. While the 

 tissue is becoming heated in the water, the 

 injection should be prepared, or be heated if 

 previously prepared, and kept constantly 

 stirred ; the stop-cocks should also be 

 immersed in hot water. 



As soon as all is ready, the stop-cock 

 turned open is fixed to the syringe and 

 some hot water is drawn into and expelled 

 from the syringe two or three times, so that 

 it may become properly heated. It is next 

 filled with the injection, taking especial care 

 that no air be allowed to enter, to avoid 

 which it must be filled, emptied and refilled 

 several times, the nozzle being kept beneath 

 the surface of the injection. The syringe is 

 then taken in the hand, a little of the injec- 

 tion being forced out at the nozzle of the 

 stop-cock, which is next loosely inserted into 

 the pipe, and some of the injection being 

 urged into it by depressing the handle, the 

 pipe is filled and the nozzle introduced into 

 it. Very gentle pressure is then made upon 

 the piston, so that the injection may be 

 driven into the vessels, and this must be 

 continued until the piston ceases to be felt 

 to move, or is seen not to enter the syringe 

 further, by watching the graduations on its 

 handle. When this is found to be the case, 

 firmer pressure must be made and the effect 

 noticed. But practice can alone guide as to 

 the time at which the pressure should cease, 

 or when as much injection has been forced 

 into the preparation as is required. Some 



judgement may be made from the colour 

 assumed by the preparation; or, the stop- 

 cock being turned off, and the syringe sepa- 

 rated from it, the preparation may be exa- 

 mined with a low power, while laid upon a 

 large glass plate. 



During the continuance of the process, 

 the preparation, the injection, and the pipes 

 must be kept at the original temperature ; 

 and should any part be found to become 

 cool, the stop-cock must be turned off, the 

 syringe separated, the injection returned to 

 the jar, fresh warm water added to the pre- 

 paration, and the whole process recommenced 

 as at first. 



If, during the process, there should be an 

 escape of the injection from any part, this 

 need not cause alarm if slight; should it, 

 however, be considerable, it must be stopped 

 by one of the means pointed out above ; 

 perhaps by the orifice of the vessel and sur- 

 rounding parts being grasped by the tena- 

 culum-forceps, and the whole included in a 

 ligature. If the preparation be small, not- 

 withstanding a considerable escape of the 

 liquid, a very good injection may often be 

 made. 



As soon as the injection is completed, a 

 ligature should be placed around the vessel 

 into which the pipe is inserted beyond its 

 nozzle ; the pipe is next removed, and the 

 preparation should be immersed in clean 

 cold water, and kept in it for an hour or two 

 at least. It may then be withdrawn and 

 sections made of it with a knife, razor, or 

 some other instrument. 



Large pieces of injected preparations are 

 best preserved in a stoppered bottle contain- 

 ing dilute spirit of wine (1 spirit to 2 water, 

 or equal parts). See also MOUNTING and 

 PRESERVATION. 



When two or more sets of vessels are to 

 be injected, the process should be continued 

 uninterruptedly until completed, *. e. as soon 

 as the injection of one set has been com- 

 pleted, another pipe should be at once 

 inserted into one of the other set, and so on. 

 Or what is better, if possible, the pipes for 

 the two or three sets should be introduced 

 and fixed at once, before the process is com- 

 menced. 



As regards the period after death at which 

 the injection should be commenced, this 

 varies with the kind of organ or tissue ; if it 

 be delicate, the sooner the better ; whilst if 

 the vessels be comparatively large, by some 

 little delay, the tissue becomes somewhat 

 softer and more yielding. 



