CHAPTER X 



FIXING; MICROTOMES AND SECTION KNIVES; IMBED- 

 DING ; SECTIONING, STAINING AND MOUNT- 

 ING ; SERIES ; MODELS 



FIXING TISSUES, ORGANS AND EMBRYOS ; MECHANICAL PREPARA- 

 TION FOR STUDY 



\ 430. Fixation. — By fixing or fixation in histology is meant the prepara- 

 tion of fresh tissues, organs, embryos or small adult animals usually by means 

 of some chemical mixture, called a "fixer" so that the organ etc as a whole 

 and the elements or cells composing it shall retain as nearly as possible the 

 morphologic characters present during life. The more perfect the fixer the 

 nearer will be the preservation of all structural details. 



Unfortunately no single "fixer" preserves with equal excellence all the 

 structural details, and therefore it is necessary to prepare the fresh tissue in 

 several different ways and to make a composite of the structural appearances 

 found, thereby approximating the actual structure present in the living body. 

 Changes are so rapid after death that the fixation should begin as soon as pos- 

 sible. For the most perfect fixation the living tissue must be put into the 

 fixer. 



-^ y ■- ^* ~3-.- 



Figs. 221-222. Class stoppered jars 

 for fixing and storing tissues for 

 histology. (Cuts loaned by I lie Whit- 

 all Talum Co.) 



With one of the larger animals where the whole animal is to be used for 

 microscopic study it is a great advantage to bring the fixer in contact with all 



