358 CONNECTIVE TISSUES. 



Table of Chemical Constitution of Fatty Substances. 



as on it depends most of the characteristic staining reactions for 

 fatty substances. 



The characteristic staining and other reactions for fatty sub- 

 stances fall into five groups : 



(1) Staining with Sudan III., or Scharlach R. 



(2) Blackening with osmic acid, either with the acid itself or 

 mixed with bichromate solution. 



(3) Staining with hsematoxylin after mordanting with bichromate. 



(4) Their behaviour in polarised light. 



(5) Staining with Nile blue. 



The rationale of these methods will now be considered. 



(1) SCHARLACH K, SUDAN III. Mixtures of the true fats, as they 

 occur in the tissues, are readily stained by these dyes. Most lipoids, 

 when pure, do not take this stain at all, or only slightly, except 

 cholesterinesters, which take the stains, although not as readily as 

 the true fats. The staining is probably a purely physical process 

 and depends on the solution of the stain in the fatty material. 

 Such solution occurs only when the fatty material is fluid, and this 

 condition is fulfilled in the tissues where mixtures of the true fats 



