PART II. 



SPECIAL METHODS AND EXAMPLES. 

 CHAPTER XXI. 



INJECTION GELATIN MASSES (WARM). 



472. Introduction. Injection masses are composed of a coloured 

 substance called the colouring mass, and of a substance with which 

 that is combined called the vehicle. 



For instructions as to the operation of injecting, and the neces- 

 sary apparatus, see the Micrographic Dictionary, RUTHERFORD'S 

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

 RANVIER, BEALE'S How to Work with the Microscope, the Lehrbmh 

 der vergleichenden Mikroscopischen Anatomic of FOL, and (for 

 apparatus especially) the article in the Encycl. d. mik. Technik. 

 For injections for the study of the angiology of Vertebrates the 

 practice of Robin and Ranvier may safely be followed. For injec- 

 tions 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 BE ALE. Glycerin masses have the great advantage that 

 they are used cold. 



All formulse which only give opaque masses, or are only suitable 

 for coarse injections for naked eye study, have been suppressed. 



In 592 is a section on injection of embryos. 



473. 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. Unfortunately, when this is done, it is 

 found that most injection masses glycerin masses especially 



