INJECTION. 



[ 425 ] 



INJECTION. 



The organ or part to be injected is then 

 immersed 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 stopcocks should also be im- 

 mersed in hot water. 



As soon as all is ready, the stopcock 

 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 special 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 

 stopcock, 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 

 judgment 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 stopcock must he turned off, the 

 syringe separated, the injection returned to 



the jar, fresh warm water added to the 

 preparation, and the whole process recom- 

 menced 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 con- 

 taining dilute spirit of wine (1 spirit to 2 

 water, or equal parts). See also PRESER- 

 VATION. 



When two or more sets of vessels are to 

 be injected, the process should be continued 

 uninterruptedly until completed; i. e. as soon 

 as the injection of one set has been com- 

 pleted, another pipe should be at once in- 

 serted 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. 



When a tissue has been successfully in- 

 jected, the vessels appear plump and well 

 filled by reflected light. But if they are not 

 so, the preparation has its value; for it will 

 perhaps well display the relative positions 

 of the capillaries to the surrounding tissues 

 when viewed by transmitted light often 

 even better than when the injection has 

 been what is termed successful. In fact, 

 when the vessels are well filled, little more 

 can be seen in general than the relative 

 situation of the vessels to each other, 



