120 PREPARATION AND MOUNTING 



would have been omitted, had it not been supposed that some 

 students might find a double pleasure in performing as much of 

 the work as possible by their own unaided labours. 



17. The process of injection may now be considered ; but it is 

 impossible for written instructions to supply the place of expe- 

 rience. I will do my best, however, to set the novice at least in 

 the right way. There are two kinds of injection one where the 

 object and colours are opaque, and consequently fit for examina- 

 tion by reflected light only ; the other, where the vessels are 

 filled with transparent colours, and must be viewed by transmitted 

 light. The first of these is most frequently employed, so we will 

 begin with it. In the object which is to be injected a vessel of 

 the kind which we wish to be filled must be found ; an opening 

 must then be made in it to allow one of the small pipes before 

 mentioned to be thrust some distance within it. When this is 

 accomplished, thread the curved needle with a piece of silk 

 thread, or very fine string, which some operators rub well with 

 beeswax. This thread must not be too thin, else there is danger 

 of cutting the vessel. The cord is then carried under the inserted 

 pipe, and the vessel bound tightly upon it, the ends being brought 

 up round the transverse arms, and there tied ; so that all danger 

 of accidentally withdrawing the pipe is obviated. Care must now 

 be used in closing all the vessels which communicate with that 

 where the pipe is placed lest the injecting fluid escape ; and this 

 must be done by tieing them with silk. Should, however, any of 

 these be left open by accident, the bullnose forceps must be made 

 use of, as before recommended. 



18. The part to be injected must now be immersed in warm 

 water, not, however, above 100 Fahrenheit, and be left until the 

 whole is thoroughly warmed. Whilst this is being done, the 

 coloured size must be made ready by the pot being placed in the 

 tin bath of warm water, which must be of sufficient temperature 

 (about 110 degrees Fahrenheit) to keep it perfectly liquid. For 

 the same purpose, the syringe is often tightly covered with two 

 or three folds, of flannel ; and, indeed, there is no part of the pro- 

 cess which requires more attention. If the substance to be in- 

 jected is too hot, it is injured ; whilst, if any of the articles are 

 too cold, the gelatine, or size, loses a part of its fluidity, and con- 



