Example 14 



Preparation of a Transverse Section of Amphioxus, Using the 

 Acid Fuchsin-aniline Blue-orange G Stain of Mallory 



Amphioxus is a difficult subject from which to prepare satisfactory sections; 

 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 secures the fixed material from using Bouin's fluid. If it is possible to se- 

 cure the living animals, they should be fixed by the methods recommended 

 for heavily muscularized material in Example 13. If this is not done, it is 

 almost impossible to secure 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 demonstration. 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 micro- 

 scope. If any selection can be exercised, care should be taken to pick a speci- 

 men of not more than 2.5 mm. thickness, in order 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 first is 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 dem- 

 onstrate, 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 Amphi- 

 oxus handled by routine methods. 



Apart from this question of fracturing of the muscular layers, no difficulty 

 will present itself in sectioning, and as many as 10- pi sections as are required 

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

 of sections from different regions of the animal, reference may be made to the 

 description of this procedure on page 131. 



When the sections have been mounted on slides, deparaffinized, and graded 

 down to water, it is recommended that they be treated overnight in a saturated 

 solution of mercuric chloride and then washed in running water for at least 

 six hours. This process improves the vividness of Mallory's stain almost beyond 

 belief when it is applied to a section of Bouin-fixed material. The solutions 

 used for Mallory's stain (see p. 25) present no difficulty in their preparation, 

 though it is recommended that 1 per cent phosphotungstic acid be substituted 



128 



