INJECTION. 



[ 353 



INJECTION. 



When a tissue has been successfully in- 

 jected, the vessels appear plump and well 

 filled by reflected light. But if they be 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. 



The choice of the kind of injection is not 

 a matter of much importance, except as 

 regards the facility with which the vessels 

 are traversed. The arteries are in general 

 filled with red injection; the veins with 

 yellow and the ducts (as the urinary tubules) 

 with white. The chromate of lead is perhaps 

 the finest injection and runs best, except 

 that made with prussian blue and oxalic 

 acid, which does not reflect enough light 

 where the vessels are to be viewed by re- 

 flected light, although when these are very 

 minute and can be conveniently viewed by 

 transmitted light, it may be preferred. 



It may be remarked, that if it be required 

 to use a yellow (the chromate) injection 

 and a white (the carbonate of lead) for two 

 sets of vessels in one preparation, the chromic 

 acid in the former must previously be com- 

 pletely neutralized, otherwise it will render 

 the white (carbonate of lead) yellow. This 

 may, however, be avoided by substituting 

 the carbonate of lime for that of lead. 



As microscopic objects, nothing can exceed 

 the beauty of injected preparations, and to 

 be seen in their greatest perfection, they 

 should be dried, moistened with oil of tur- 

 pentine and mounted in Canada balsam. At 

 the same time it must not be forgotten that 

 when dried and preserved in this manner, 

 the real arrangement of the vessels is more 

 or less distorted, those lying in different 

 planes being brought into the same, and so on. 



In Plate 31. figs. 33, 34 and 35, we have 

 given representations of three injections 

 viewed by reflected light; fig. 35 being taken 

 from the liver of a cat, in which injection 

 made with vermilion was thrown into the 

 portal vein, and that with chromate of lead 

 into the hepatic vein. Fig. 34 is a portion 

 of the lung of a toad injected with vermilion; 

 and fig. 35 is a portion of the kidney of a 

 pig, the arteries and Malpighian tufts 

 (KIDNEY) being filled with the red (vermi- 

 lion) injection, and the urinary tubules with 

 the white (carbonate of lead). 



The tissues of the Invertebrata are so soft, 

 that the ordinary syringes and pipes can 

 rarely be used for injecting them, and re- 

 course must be had to a finer and lighter 

 form of apparatus. One recommended by 

 Rusconi consists of a kind of trochar, con- 

 sisting of a needle and the quill of a crow, 

 partridge, or some small bird. In using it, 

 the small vessel through which the injection 

 is to be thrown is held with forceps against 

 the extremity of the trochar, and punctured 

 with the needle. The quill is next directed 

 into the puncture, and the needle withdrawn. 

 The small nozzle of a syringe is then intro- 

 duced into the upper end of the quill, and 

 the injection thrown in. A form proposed 

 by Harting consists of a common glass pi- 

 pette of moderate width, and of a caoutchouc 

 tube, the smaller end of which is fastened by 

 means of thread to the broader end of a fine 

 curved glass nozzle. In using this apparatus, 

 the pipette is first filled with the injection, 

 and its lower portion introduced into the 

 broader end of the caoutchouc tube, which, 

 from its conical form, it accurately closes. 

 The caoutchouc tube may be made by rolling 

 a piece of sheet caoutchouc around a glass 

 rod, and cutting the superfluous portions 

 away with scissors ; the freshly divided sur- 

 faces will adhere by a little kneading with 

 the nails, and they may be secured by solu- 

 tion of caoutchouc or gutta percha in oil of 

 turpentine. 



Different liquids for injection are also usu- 

 ally requisite, and many have been recom- 

 mended ; among these may be mentioned, 

 1, indigo triturated with oil, and diluted 

 with oil of turpentine ; 2, oil-paints diluted 

 with oil of turpentine; 3, infusion of log- 

 wood (H&matoxylon) ; 4, solution of carmine 

 in size or in ammonia ; and 5, solution of 

 alkanet in turpentine. 



A considerable escape of the injection is 

 often unavoidable in these cases, and must 

 not therefore be heeded. 



Some injectors simply introduce the in- 

 jection into the dorsal vessel or lacunae, 

 whence it is propelled to all parts of the 

 body by the circulation. Thus M. Agassiz 

 says that if the indigo injection (1) be intro- 

 duced in this way into insects, it is seen to 

 circulate almost instantaneously in every 

 part of the body, and on subsequently open- 

 ing the insect, all parts of the body are found 

 to be coloured. We believe that M.Blanchard 

 also adopts this method. Probably the best 

 injections for this purpose would consist of 

 the alkanet and turpentine (5). 



2 A 



