INJECTION. 



[ 350 ] 



INJECTION. 



Sometimes a much smaller syringe, called 

 an oyster-syringe, is useful for injecting very 

 small and soft animals. 



The plug of the piston is adapted to the 

 tube of the syringe by two pieces of wash- 

 leather, the method of replacing which must 

 be learnt at the time the syringe is bought, 

 for it is difficult of description. The plug 

 must work air-tight in the tube, which may 

 be proved by depressing the handle as far as 

 possible, then closing the nozzle of the sy- 

 ringe with one finger, withdrawing the han- 

 dle to its fullest extent, and letting it go, 

 when it should fly entirely home. If this 

 does not take place, the plug must be re- 

 leathered. 



The handle of the syringe should be gra- 

 duated, i. e. transverse lines should be 

 scratched upon it with the end of a file, or 

 in some other way, so that when its descend- 

 ing movement is so slow as not to be felt 

 by the hand, it may be indicated to the 

 eye. 



The syringes, and in fact all the mechani- 

 cal apparatus requisite for injection, may be 

 purchased of Mr. Neeves, High Street, Hoi- 

 born, or of Mr. Ferguson, Giltspur Street, 

 Smithfield. 



The syringe must accurately fit the stop- 

 cocks and pipes. 



Injecting pipes. These must be of various 

 sizes, to suit those of the vessels into which 

 they are to be introduced ; they are furnished 

 with two short transverse arms, by which 

 they may be tied to the vessel. The smallest 

 pipes which are made easily become stopped 

 up unless thoroughly cleansed after use ; to 

 remove any obstruction, a very fine kind of 

 needle made of watch-spring is required, 

 and may be procured of Mr. Ferguson as 

 above. 



Stop-cocJcs. One or two of these are use- 

 ful in stopping the injection from returning, 

 when the syringe is removed, or force ceases 

 to be applied to it. 



Forceps. One or two pairs of small tena- 

 culum forceps must be at hand; these are 

 noticed in the INTRODUCTION, p. xxii. 



Jars or other vessels for holding the in- 

 jection. These may consist of confectioners' 

 jam-pots, or may be made of tin. The for- 

 mer have the advantage of retaining the heat 

 for a considerable time. When in use, the 

 jars must be placed in a water-bath, or in a 

 tin vessel containing water, and placed over 

 a stove. 



Stirring -rods. These must be made of 

 wood. 



Size. The colouring matters used for in - 

 jection are mostly insoluble powders. These 

 are usually mixed with size or some form of 

 solution of gelatine, which holds them in 

 suspension better than water. The author 

 of the application of this substance to in- 

 jecting purposes we believe to be Mr. Goadby, 

 and very valuable it is. 



The size mostly used is that termed Young's 

 patent size, and it is sold in the shops. It 

 should be clear and fresh. Those who can- 

 not obtain this may prepare its equivalent 

 by dissolving 1 part of glue in 8 or 10 parts 

 of water with the aid of heat. 



The principal liquid injections used may be 

 arranged according to their colours. In re- 

 gard to the proportions of the colouring mat- 

 ter to that of the size, it must be remarked 

 that these vary as used by different injectors; 

 and that, in general, when the vessels to be 

 injected are very minute, the size should be 

 somewhat thinner, and the proportion of 

 pigment rather less than under the opposite 

 conditions. When the injection is directed 

 to be strained, this must be done through a 

 piece of new flannel wrung out of hot water, 

 or through a ' tammy sieve,' which is more 

 convenient. In preparing the injections, 

 great care must be taken that the jars are 

 perfectly clean, and that no old injection 

 remains adherent to them. The colouring 

 matters, whether dry or dissolved, should be 

 added to the size previously warmed in the 

 water-bath, or the tin vessel mentioned 

 above, and the whole should be stirred until 

 thoroughly incorporated. When trituration 

 is spoken of, it must be understood that the 

 rubbing in a mortar should be continued for 

 a long time, until the substance is reduced 

 to the finest possible state of powder. 



Harting recommends preparing a stronger 

 size than that mentioned above, containing 

 1 part of glue to 4 of water, and that the 

 chemical substances be dissolved in the ad- 

 ditional water requisite before being added 

 to the size, which would seem to be prefer- 

 able ; but we have found the method recom- 

 mended to answer every purpose, and it has 

 the advantage of greater simplicity. 



Red Injection. This is best made with 

 vermilion (bisulphuret of mercury), which 

 before use should be carefully examined as 

 to its purity from minute colourless crystal- 

 line particles, by viewing it by reflected light, 

 when they are easily detected. When the 

 vessels to be injected are very minute, the 

 vermilion is best previously levigated, i. e. 

 triturated in a mortar with a small quantity 



