The Interstitial Granules of Striated Muscle etc. 307 



the large Q-granuIes of insect muscle, are- not shown in potassium 

 hydroxid. Faintly-refractive granules sometimes disappear rapidly, 

 especially if the stronger solutions are used. In order to examine the 

 faintly-refractive granules satisfactorily it is sometimes best to mount 

 the specimen in distilled water and then draw a 1 per cent solution of 

 the alkali slowly under the cover glass with a piece of filter paper- 

 watching the specimen meanwhile witii the high power. Very faint 

 granules are sometimes visible only a short time. 



d) Osmic acid. I now use this in the form of Altmann's solution 

 (equal parts of 2 per cent osmic acid and 5 per cent potassium bichro- 

 mate). A simple solution of osmic acid sometimes forms precipitates 

 when tissues are exposed 24 hours or longer; but with Altmann's solution 

 this source of error is avoided. The solution was used mainly on frozen 

 sections and on teased preparations, but some pieces of tissue were 

 fixed and embedded in paraffin. A large proportion of the liposomes 

 are not stained at all by this reagent. A great many are colored varying 

 shades of brown, and only a small per cent are stained black. The 

 degree of staining depends upon the species of the animal, its nutritive 

 plane, etc. An exposure of 24 hours is required to get the full effect of 

 the stain. The tissues to be embedded in paraffin were cleared in cedar 

 oil— if xylol is used most of the brown granules are lost. Even when cedar 

 oil is used many of the light brown granules are frequently lost. 



e) Simple alcohohc solutions of scarlet red or Sudan III, These 

 are saturated solutions prepared by dissolving the dye in cold or boiling 

 70 to 80 per cent alcohol. Very variable results have been obtained 

 with these stains. At one time I regarded the solutions in cold alcohol 

 as worthless; but I have lately obtained excellent results by using a 

 large excess of scarlet red in 80 per cent alcohol (2 grams of the dye to 

 100 ccm of 80 per cent alcohol). These solutions will often stain 

 liposomes that are not colored by osmic acid. They are however never 

 as good as the alkaline solutions since they do not clear up the tissue. 

 (See appendix). 



f) Alkaline-alcoholic solution of scarlet red (Herxheimer's stain). 

 This is a very strong solution. When properly used it apparently stains 

 all the interstitial granules in vertebrate muscle that are visible in fresh 



20* 



