46 CELL-CONTENTS AND CELL-WALLS. 



with (1) iodine solution the grains turn yellow ; (2) dilute 

 potash the crystalloids swell and dissolve, leaving the 

 globoids behind ; (3) dilute sulphuric acid (note that this 

 destroys the grains), then iodine solution (this stains the 

 matrix left behind in the cells) ; (4) a drop or two of 

 1 per cent, osniic acid the crystalloids slowly swell, while 

 the rest of the cell- contents, especially the oily matrix, 

 rapidly becomes blackened. 



(e) Cut dry sections, and transfer them to a watch-glass 

 containing two parts of alcohol and one part of castor oil, 

 with enough eosin to make the mixture light red. After 

 a few hours, mount in castor oil and alcohol (without the 

 eosin) . This treatment brings the grains out clearly ; they 

 are seen embedded in vacuoles in the cytoplasm of the cells. 



(/) Place some dry sections in alkannin ( 86) for 

 several hours, and mount in dilute glycerine ; the oil is 

 stained red. 



(g) The structure of the grains is well brought out by 

 fixation in alcoholic picric acid, and staining with eosin. 

 Place the sections in concentrated alcoholic solution of 

 picric acid in a watch-glass for several hours ; then wash 

 them in alcohol, and stain for a few minutes in eosin 

 dissolved in alcohol. It is best to wash the sections next 

 in absolute alcohol, transfer them to oil of cloves, and 

 mount in Canada balsam. The matrix of the grains is 

 stained dark red, the crystalloid yellow, and the globoid 

 remains colourless. 



(h) Note that the globoids are (1) insoluble in alcohol 

 and in dilute potash, but (2) soluble in dilute mineral 

 acids (hydrochloric, nitric, or sulphuric) and in acetic 

 acid ; (3) in an ammoniacal solution of ammonium phos- 

 phate the globoids are replaced by crystals of ammonium 

 magnesium phosphate ; (4) on being treated with am- 

 monium oxalate, they are replaced by crystals of calcium 

 oxalate ; (5) after extracting the oil from sections by treat- 

 ment with alcohol, or alcohol and ether, the globoids can 

 be made to stand out clearly on adding some dilute ( 1 per 

 cent.) potash solution which will dissolve the ground sub- 

 stance of the protein grains, 



