The Interstitial Granules of Striated Muscle etc. 321 



osmic acid ; but that there are other fats is shown by the staining of 

 the medullary substances. We cannot say that all osmic-staining fat 

 is oleic acid or triolein. 



The intensity of the osmic stain varies from an intense black to a 

 very faint gray. How is this to be explained ? The most probable ex- 

 planation seems to be the one suggested by Handwerck's results. The 

 intensity of the stain is in proportion to the percentage of oleic fat 

 present. Droplets that stain brown or grey contain less oleic fat than 

 those that stain black. But it is to be remembered that there may be 

 other fats that can cause this color. 



There are a great many liposomes that cannot be stained at all by 

 osmic acid. What is their composition ? These hposomes are soluble in 

 ether and absolute alcohol, and may be stained with scarlet red (at 

 least with the alkahne solutions). They must therfore be regarded as 

 composed of fatty substances. Altmann called attention to the large 

 droplets in the Harderian gland of the rabbit that do not blacken in 

 osmic acid. These stain intensely with scarlet red and sudan III, and 

 are readily soluble in alcohol and ether. 



I have tested the muscle liposomes (not stainable with osmic acid) 

 and the Harderian gland of the rabbit with the solutions of Benda and 

 Klotz. The results were always negative showing the absence of fatty 

 acids and soaps. It is also certain that these droplets cannot to any con- 

 siderable extent consist of palmatin and stearin, since they do not form 

 crystals when the temperature is reduced nearly to freezing. Palmatin 

 and stearin would crystallize readily at room temperature since the 

 melting point of each is far higher. Of course if the liposome contains 

 a considerable amount of low-melting fat the higher melting fats may 

 be held in solution. Altmann suggested that butyrin might compose 

 the fat of the Harderian gland of the rabbit, since it is a low-melting 

 fat and does not reduce osmic acid. All we can say at present of lipo- 

 somes that do not reduce osmic acid is that they must consist mainly 

 of some low-melting fat other than olein. 



In the light of the facts Just given we cannot agree with Mulon 

 that the droplets that stain grey or brown with osmic acid consist 

 mainly of palmatin and stearin. It seems more probable that these 



Internationale Monatsschrift f. Anat. u. Phys. XXVIII. 21 



