INJECTION. 



[ 426 ] 



INJECTION. 



The choice of the kind of injection is not 

 a matter of much importance, except as 

 regards the facility with which the vessels 

 are filled. 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 completely neutralized; otherwise it will 

 render the white (carbonate of lead) yellow. 

 This may, however, be avoided by substi- 

 tuting the carbonate of lime for that of lead. 



As microscopic objects, nothing can ex- 

 ceed the beauty of injected preparations; 

 and to be seen in their greatest perfection 

 they should be dried, moistened with oil of 

 turpentine, and mounted in Canada balsam. 

 At the same time it must not be forgotten 

 that, when dried and preserved in this man- 

 ner, the real arrangement of the vessels is 

 more or less distorted, those lying in dif- 

 ferent planes being brought into the same, 

 and so on. 



In Plate 39. figs. 33, 34, and 35, we have 

 given representations of three injections 

 viewed by reflected light, fig. 33 being 

 taken from the liver of a cat, in which in- 

 jection 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 

 (vermilion) injection, and the urinary tu- 

 bules with the white (carbonate of lead). 



Self-injection occupies an important posi- 

 tion amongst the various modes. The vas- 

 cular system of the frog may be injected by 

 inserting a pointed glass tube filled with 

 the coloured injecting fluid into the vena 

 cava. The fluid passes into the heart, and 

 is distributed through the system by the 

 force of the heart itself. The biliary vessels 

 of living animals have been injected by 

 means of colouring-matter introduced into 

 the jugular veins. 



Toldt has injected the lymphatics on this 

 system ; and he introduces a granular pig- 

 ment (aniline) precipitated by water from its 

 alcoholic solution into the blood. 



The perfect injection of an organ or an 

 entire animal of considerable size is a 

 tedious and fatiguing process. We have 

 therefore contrived a very simple piece of 

 apparatus, which any one can prepare for 

 himself, and which effects the object by 

 mechanical means. It consists of a rect- 

 angular piece of board, 2' long and 10" wide, 

 to one end of which is fastened an inclined 



Fig. 360. 



piece of wood supported by two props, as 

 shown in fig. 360. The inclined portion is 

 pierced with three holes, one placed above 

 the other, into either of which the syringe 

 may be placed the uppermost being used 

 for the larger, the lowermost for the smaller 

 syringe ; and these holes are of such size as 

 freely to admit the syringe covered with 

 flannel, but not to allow the rings to pass 

 through them. The lower part of the 

 syringe is supported upon a semiannular 

 piece of wood, fastened to the upper end of 

 an upright rod, which slides in a hollow 

 cylinder fixed at its base to a small rect- 

 angular piece of wood ; and by means of a 

 horizontal wooden screw, the rod may be 

 made to support the syringe at any height 

 required. The handle of the syringe is let 

 into a groove in a stout wooden rod con- 

 nected by means of two catgut strings with 

 a smaller rod, to the middle of which is 

 fastened a string playing over a pulley, and 

 at the end of which is a hook for supporting 

 weights, the catgut strings passing through 

 longitudinal slits in the inclined piece of 

 wood. 



In use, the part to be injected is placed 

 in a dish of some kind containing warm 

 water, supported at a suitable height beneath 

 the end of the syringe by blocks of wood. 

 The syringe is then filled with injection, 

 passed through the proper aperture in the 



