EXAMPLE 16 



Preparation of a Transverse Section of Amphioxus, 



Using the Acid Fnchsin- Aniline Blue-Orange 



G Stain of Mallory 



Amphioxus is a difficult subject from which to prepare satisfactory sec- 

 tions; the more so as it is almost impossible nowadays to secure supplies 

 of living Amphioxus and to fix them oneself, or to prevent the supplier 

 from whom one obtains the fixed material from using Bouin's fluid. If it is 

 possible to get the living animals, they should be fixed by the methods 

 recommended for heavily muscularized material in Example 15. If this is 

 not done, it is almost impossible to obtain unbroken sheets of muscle 

 in the transverse section unless one is prepared to sacrifice a certain 

 amount of histological detail in the interest of morphological demonstra- 

 tion. It is also greatly to be regretted that popular demand has forced the 

 biological supply houses to sell only the very large specimens, with the 

 result that the sections are too large to be viewed at one time in even the 

 lowest power commonly available on a student microscope. If any selec- 

 tion can be exercised, care should be taken to pick a specimen of not 

 more than 2.5 mm thickness, so that it may be seen as a whole. 



If, however, one is forced to use a Bouin-fixed specimen, it may be 

 sectioned without too much difficulty, provided that it is first soaked 

 overnight in 1 per cent nitric acid. This treatment naturally destroys 

 much of the fine cytological detail and should not be applied to any 

 specimen in which it is desired to demonstrate, for example, the detailed 

 structure of the endostyle. The author, however, is always prepared to 

 sacrifice such detail as this in a section desired for class demonstration 

 to avoid having to answer endless questions as to what is this and that 

 cavity, which will be seen in a section of Bouin-fixed Amphioxus handled 

 by routine methods. 



Apart from this question of fracturing of the muscular layers, no diffi- 

 culty will present itself in sectioning, and as many 10-//. sections as are 

 required should be accumulated. If it is desired to place on the same slide 



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