362 



CONNECTIVE TISSUES. 



The Myelin and Potential Fluid Crystalline Bodies of the Organism, 

 1906 ; KAISERLING and OGLER, " Uber das Auftreten von Myelin 

 in Zellen, etc.," Vir chow's Archiv., clxvii.). 



(5) NILE BLUE. When a solution of Nile blue is boiled with 

 sulphuric acid the solution contains, in addition to the original basic 

 oxazine dye, which unites with fatty acids to form a blue compound, 

 a red oxazone dye, not basic in character, but soluble in liquid fat 

 and giving it a red colour. The stain, therefore, enables us to 

 distinguish neutral fat and fatty acid. If a given globule contains 

 neutral fat and no fatty acid, it will be coloured red ; if it contains 

 fatty acid only, it will be coloured blue ; but if it contains both 

 neutral fat and fatty acid, it will be coloured a tint between blue 

 and red, depending on the proportion of neutral fat and fatty acid. 

 The principal histochemical group reactions are summarised in the 

 following table : 



Table of some important Histochemical Group Reaclions. 



Although different groups of fatty substances differ in their 

 behaviour towards different staining methods, it is, nevertheless, 

 necessary to proceed with caution in interpreting the results obtained 

 when these methods are applied to tissues. In the tissues the various 

 groups of fatty substances are mixed, so that one globule may contain 

 two or three different substances. The various substances may 

 then form a special kind of colloidal solution, which modifies their 

 physical state and alters their staining reaction completely. The 

 behaviour of mixtures of cholesterin and fatty acids is an example 

 and has been referred to above. Or one substance encloses another 

 substance belonging to a different group. In such a case the 

 staining reactions of the globule would be those of the material 

 which constitutes the envelope. In the adrenal cortex, for instance, 



