STAINING, PRACTICAL AND THEORETICAL 



him in the same paper and which are described briefly on pages 

 336-7 of this book. It is stated that the Sudan black method 

 shows cellular detail more clearly, and also all the stages in the 

 cytomorphosis of the interstitial cell, but that it does not demon- 

 strate the development of secretory granules: these, however, 

 are well shown by the osmic acid method. 



(c) The author states that the testis of a number of birds have 

 been treated by his Sudan black technique, and that numerous 

 dark blue granules in contact with small vacuoles (from which 

 the lipid secretion droplets have been dissolved out during wax 

 embedding) occur in the cytoplasm of the interstitial cells of 

 birds. These granules are considered to be mitochondria. 



(d) Counterstaining with Ehrlich haematoxylin or with eosin in 

 30% alcohol was found to obscure the results, although the eosin 

 was found to give a fair contrast. 



(e) It was found that sections took twenty-four hours to clear 

 in Farrants' medium, and that it is advisable to hold the coverslip 

 in place with a spring clip during that time. 



(/) Readers should consult the original paper for more detailed 

 information and photomicrographs. 



Reference: Threadgold, L. T. (1957). 



SUDAN BLACK 



For lipids (especially those that are not well coloured by 



Sudan III or IV) 



(J. R. Baker's technique) 



Solutions required: 



A. Formaldehyde-saline. 



Formalin (Formaldehyde 40%) . . 10 ml. 

 Sodium chloride 10% aqueous . . 7 ml. 

 Distilled water . . . . • • 83 ml. 



Note: Keep a few pieces of marble chips in 

 the solution to maintaifi neutrality. 



B. Formalin (Formaldehyde 40%) neutral. 



Note : Keep a few pieces of marble chips in 

 the bottle. 



424 



