SECTION SEVEN 



4. Drain off excess water ; blot and dry. 



5. Mount in glycerine and examine under the oil-immersion 

 objective. 



Results: 



Erythrocytes from haemorrhage more than twenty-four hours 

 old appear with ring-like peripheries and unstained centres, while 

 those from fresh haemorrhage in the cerebrospinal fluid are stained 

 yellow. 



SUDAN 3 

 For staining fat in faeces 



Solution required: 



Sudan 3 saturated in equal vol- 

 umes of 70% alcohol and ether. 



Technique: 



1. A loopful of faeces is mixed with a drop of 50% alcohol. 



2. Add one or two drops sudan 3 solution ; then apply a cover- 

 glass before examining. 



Results: 



Neutral fat appears as highly refractile droplets or yellowish 

 flakes which stain orange to orange-red. 



Note: In normal faeces there is no appreciable amount of 

 neutral fat present. 



Fatty acids appear as flakes, which stain faintly; or as fine 

 needles which tend to collect in clusters and do not take the stain. 



Soaps appear as yellowish flakes, rounded or gnarled bodies, 

 everted like the pinna of the ear, or as coarse crystals, which do not 

 take the stain. 



On warming the preparation gently, fatty acids melt, whereas 

 the soaps do not. 



In the faeces of a healthy subject the only fat elements recog- 

 nizable under the microscope are yellow calcium or colourless 

 soaps. 



399 



