CHAPTER XXI. 



INJECTION GELATIN MASSES (WAEM). 



480. Introduction. Injection masses are composed of a 

 coloured substance called the colouring mass, and of a sub- 

 stance with which that is combined called the vehicle. 



For instructions as to the operation of injecting, and the 

 necessary apparatus, see the Micrographic Dictionary, RUTHER- 

 FORD'S and SCHAFER'S Practical Histology, the treatises of 

 ROBIN and RANVIER, BEALE'S How to Work with the Micro- 

 scope, the Lehrbuch der vergleichenden Mikroscopischen Ana- 

 tomie of FOL ; and (for apparatus especially) the article in the 

 Enci/cl. d. mik. Technik. For injections for the study of the 

 angiology of Vertebrates the practice of Robin and Ranvier 

 may safely be followed. For injections of Invertebrates (and 

 indeed, for vertebrates if it is desired to demonstrate the 

 minute structure of environing tissues at the same time as 

 the distribution of vessels) masses not containing gelatin 

 are, I think, generally preferable to gelatin masses ; and I 

 would recommend as particularly convenient the Prussian 

 blue glycerin masses of BEALE. Glycerin masses have the 

 great advantage that they are used cold. 



All formulae which only give opaque masses, or are only 

 suitable for coarse injections for naked eye study, have been 

 suppressed. 



481. Vaso-dilators. In order that an injection may run 

 freely it is necessary that the vessels of the subject be in a 

 relaxed state. To this end the older anatomists used to wait 

 until rigor mortis had passed off before injecting. But it is 

 evidently preferable in the interest of the proper preservation 

 of the tissues to inject before rigor mortis has set in. Un- 

 fortunately, when this is done, it is found that most injection- 



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