SECTION TWO 



22. Blot away excess water but do not allow the section to dry. 



23. Mount in Farrants' medium, or in Aquamount. 



24. Attach a clip to hold the coverslip to the slide : then leave 

 overnight in the oven to harden the mounting media, before 

 examining the preparation under the oil immersion objective. 



Note: The slide may be examined after a quarter of an hour, if 

 desired; then returned to the oven to complete the hardening. 



Results: 



Lipids, dark blue or blue-black. Cytoplasm : colourless or pale 

 grey-blue. Chromatin: pink or red. 



Note: If the results are not good, another section should be tried 

 with variations of the staining times. 



Never attempt to judge the colouring until the section is 

 mounted and examined under the oil immersion objective. 



It is recommended that the technique be learned on the intestine 

 of the mouse, as it is scarcely possible to fail with this. Cut out a 

 piece of empty intestine about i cm. long and immerse in for- 

 maldehyde-saline for five minutes, then open it by a longitudinal 

 cut from one end to the other, taking care not to do any unneces- 

 sary damage to the villi. 



The section should be left only one minute in the Sudan black 

 and two and a half minutes in the carmalum. 



References : 



Baker, J. R. (1949). 



Baker, J. R. (1955), personal communication. 



SUDAN BLACK 

 For myelin and neutral fats 



Solutions required: 



A. Sudan black, saturated in 70% 



alcohol or 70% ethylene glycol 



B. Carmalum (Mayer) 



Technique: 



Tissues are fixed at least three days in 10% formalin; then 

 rinsed thoroughly in distilled water. 



1. Frozen sections are immersed one minute in 50% alcohol; 

 then one minute in 70% alcohol. 



2. Stain for fifteen minutes to several hours in the Sudan black. 



427 



