6 H. HAYS BULLARD 



number of facts relating to the optical, chemical and physical 

 properties exhibited by pure fats and fatty mixtures when ob- 

 served, after being artificially introduced into the tissues or when 

 studied as smears on tissue paper. Application of the knowledge 

 thus gained makes possible, in certain cases, the identification of 

 various fats as they occur in the tissues. 



Figures 1, 2, 3, 4, and 5 represent sections of the myocardium 

 of rats, figure 10 is from a dog and figure 9 from a fattened hog. 

 The preparations were stained with Herxheimer's Scharlach R. 

 The number of normal hearts which I have examined by this 

 method is more than two hundred and always with results simi- 

 lar to those represented in the figures. It is of course well recog- 

 nized that Scharlach R. is not specific for neutral fat. Never- 

 theless, I believe that the colored droplets shown in these figures 

 are, at least in very large part, neutral fat. The reasons for this 

 belief as outlined below are essentially those advanced in a former 

 paper ('12 a). Concerning similar fatty droplets in cardiac 

 muscle Wegelin ('13), likewise, has come to the conclusion that 

 they are neutral fat and for much the same reasons. 



In unstained preparations these droplets are to be seen as 

 approximately spherical, highly refractive, isotropic bodies which 

 do not disappear in acetic acid or in dilute alkalies, orm no 

 myelin figures, but are completely dissolved by absolute alcohol 

 and other fat solvents. They stain characteristically with 

 Scharlach R. and stain red, not blue, with nile blue sulphate and 

 nile blue chlorhydrate. They do not stain with basic anilin 

 dyes and are not rendered insoluble by the action of potassium 

 bichromate. The above combination of properties makes it 

 appear certain that the droplets under consideration are neutral 

 fat and not any of the other fats occurring either normally or 

 pathologically in cardiac muscle as, phospholipines, cholester- 

 inester, etc. 



