358 



CONNECTIVE TISSUES. 



Table of Chemical Constitution of Fatty Substances. 



Group. 



True fats . 



Simple 



lipoids. 

 Sterines. 



Phospha- 

 tides 

 (phos- 

 phorised 

 fats). 



Cerebro- 

 sides. 



Compound 

 lipoids. 

 Phospho- 



rised 



cerebro- 



sides. 



Examples. 



Palmitin. 



Stearin. 



Olein. 



(A.) Cholesterin 

 (Cholesterol). 



(B.) Cholesteri- 

 nesters. 



Lecithin. 

 Kephalin. 



Cerebron 



(Cerebrin, 



Phrenosin). 



Homocerebrin 



(Kerasin). 



Protagon. 



Characteristic central 

 groups. 



Glycerine and fatty acids. 

 'ii 



(A.) Cholesterin free. 



ii 



(B.) Cholesterin and fatty 

 ii acids, 



ii 



Glycerine, phosphoric acid, 

 and fatty acids, 

 'ii 



Galactose and a fattv acid. 



A chemical combination 

 of the two cerebrosides, 

 cerebrin and homocere- 

 brin (vide supra), and a 

 substance sphingomye- 

 lin, allied to the phos- 

 phatides (see next 

 column). 



Additional groups. 



None. 



None. 



A nitrogenous base, 

 e.g., cholin in the 

 case of lecithin. 



The nitrogenous base 

 sphingosin. 

 ii 



Sphingomyelin, which 



contains phosphoric 



acid, a fattv acid, 



sphingosin and cholin 



ii ii 



Solubilities. 



Readily soluble in ace- 

 tone, ether, chloro- 

 form and benzene. 



(A.) Same as true fats. 



(B.) Not readily soluble 

 in alcohol and ace- 

 ton, soluble in ether, 

 chloroform and ben- 

 zene. 



Not soluble in acetone, 

 readily soluble in 

 alcohol, ether, chloro- 

 form and benzene. 

 Kephalin, when pure, 

 is insoluble in alcohol. 



Insoluble in fatty sol- 

 vents in the cold ex- 

 cept pyridine. Soluble 

 in hot alcohol, ben- 

 zene, chloroform. 



Same as cerebrosides. 



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 R, 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 



