318 E. T. Bell, 



results on smears of ordinary connective tissue fat, olive oil, oleic acid, 

 sodium oleate, medullary sheaths of nerve fibers, cerebrin, palmitic and 

 stearic acids. The color obtained by the alkaline stain is usually a 

 deeper red. The main difference between these stains seems to be 

 in intensity of staining, such as is found between dilute and concen- 

 trated haematoxylin. The alkaline solution is more highly saturated 

 and gives up the dye more readily, as is shown by its greater tendency 

 to form precipitates. It is to be expected then that it should be capable 

 of detecting traces of fat that a weaker stain would miss. If it be true that 

 the faintly-refractive liposomes contain a smaller proportion of fatty 

 substances it is easy to understand how they are so frequently missed by 

 the simple alcoholic solutions, but shown by the alkaline alcoholic stain. 



Both the simple and the alkaline-alcoholic solutions stain a large 

 number of liposomes that are unaffected by osmic acid. They also color 

 intensely the large fat droplets in the Harderian gland of the rabbit, 

 tho these are not stained at all by osmic acid. 



3. Osmic. acid. Sometimes (some cats and dogs) a muscle is found 

 in which this reagent will blacken every liposome that can be shown by 

 any other method, but such instances are rare. As a rule it fails to stain 

 a large proportion of the liposomes. Faintly-refractive liposomes are 

 usually not colored at all ; but sometimes (as in the frog and rat) some 

 of them may be stained a faint brown. The strongly-refractive liposomes 

 are usually colored black; and those that are moderately-refractive 

 may be stained varying shades of brown or grey. But muscles are often 

 found (some young pups, rats, and cattle) containing a large number of 

 moderately- or even strongly-refractive liposomes that are not stained 

 at all by osmic acid. It is well known that the large fat droplets in the 

 Harderian gland of the rabbit are not stained at all by osmic acid, tho 

 they are intensely colored by scarlet red and sudan III. There are 

 therefore fats that are not stained by osmic acid. 



What fats are stained by osmic acid ? Altmann (1894) has shown 

 that this substance is not a reagent for fats in general. He found that 

 oleic acid and triolein are blackened by it, but that palmatin and stearin 

 and their acids, lecithin, and solium oleate are colored only a light gray. 

 Bîïcyrin does noi reduc*^ osmic acid. 



