236 Specific Examples of Slide Making 



a collection of sections from different regions of the animal, reference may 

 be made to the description of this procedure in Example 18. 



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 6 hr. 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 present no difficulty in 

 their preparation, although it is recommended that 1 per cent phospho- 

 tungstic acid be substituted for the 1 per cent phosphomolybdic acid spec- 

 ified in the original method. The sections, when they have been washed 

 thoroughly after the mordanting in mercuric chloride, are placed in the 

 1 per cent solution of acid fuchsin for a period of about 2 min. This time 

 is not critical; it is necessary only to make sure that the entire section 

 is thoroughly stained. On removal, the sections are rinsed rapidly in water 

 for the purpose of removing the surplus stain, and then are placed in the 

 1 per cent phosphotungstic acid until such time as the red stain has been 

 removed entirely from the connective tissues. This may be judged partly 

 by the cessation of the color clouds that rise from the section and partly 

 by an examination under the lower power of the microscope to make sure 

 that the septa between the myotomes are free from color. The specified 

 time of 2 min is usually sufficient, and the sections will not be damaged 

 however long they may be left. On removal from this solution, they are 

 rinsed quickly in water and placed in the acid-methyl blue-orange G 

 solution where they should remain for at least 15 min. The mistake is often 

 made of leaving them for too short a time in this stain, for they will have 

 the appearance of being deeply stained after an immersion of only a few 

 moments. It does not matter how long they remain; it is the author's 

 experience that soaking for at least 15 min discourages the subsequent 

 removal of the blue from the tissues. After they are removed from this 

 rather thick staining mixture, the slides are washed thoroughly in water. 

 This wash is designed to remove not only the whole of the adherent stain 

 from the slide but also to permit the oxalic acid to be leached out of the 

 tissues. No "differentiation" of the stain should take place in water, 

 since the necessary differentiation is produced by the absolute alcohol 

 used for dehydration in the next stage. It is quite impossible to take sec- 

 tions stained by this method up through the common graded series of 

 alcohols, but no grave damage will be occasioned by the omission of this 

 step. If, however, the operator is one who insists that his sections pass 

 through a graded series, mixtures of acetone and water should be sub- 

 stituted for alcohol and water. When the sections reach absolute alcohol, 

 they should be watched very closely, while being moved continuously up 

 and down in the alcohol. The blue color will leave them in great clouds; 



