REACTIONS OF PBOTEIDS. 35 



substance of the grain from the protein enclosures. The body 

 substance of a protein grain consists of proteids of various degrees 

 of solubility. In many seeds, as in the Pseony, the grains are 

 wholly soluble in water ; sections of such seeds would need to be 

 examined in glycerine, or in alcohol, or other non-watery reagent ; 

 and if water be then drawn under the cover-glass, their gradual 

 solution may be observed. Other grains are only partly soluble, 

 or are wholly insoluble, in pure water, but these insoluble parts, 

 or grains, can be dissolved by dilute caustic soda (1-2 per cent, 

 solution). Some methods of permanent preparation of stained 

 sections are based upon the fact that the grains can be made 

 insoluble, as, e.g., by treatment for a few hours with alcoholic 

 solution of picric acid, or of corrosive sublimate. This body 

 substance of the grain is bounded externally, and also internally 

 if there be enclosures, by a thin pellicle composed of a more 

 insoluble form of protein matter, which is made very visible by 

 the solution of grain and enclosures. The crystalloids are never 

 soluble in water, and on the partial solution of the aleurone 

 grains in this they show up very clearly. They have about the 

 same refractive characters as glycerine, and hence (unless stained) 

 are not usually visible in this or in alcohol as a mountant. They 

 are soluble in dilute caustic potash. 



The crystalloids can be well stained with eosin, particularly 

 if the sections have been previously fixed by soaking for at least 

 twelve hours in concentrated alcoholic solution of corrosive 

 sublimate, and the sublimate washed out with alcoholic solution 

 of iodine of a dark sherry-brown colour ; but if this is not care- 

 fully done needle- or sphere-crystals of the sublimate may be 

 formed. A solution of eosin in absolute alcohol is used and 

 allowed to act for a few minutes. The section can then be put 

 up as a permanent preparation, in Canada balsam, in the manner 

 detailed below, when the ground substance will be seen to be 

 stained dark red, and the protein crystal yellow, while the globoid 

 is nearly colourless. 



Logwood (Haematoxylin) added in small quantity to a pre- 

 paration in glycerine stains the protein crystals and aleurone 

 grains a beautiful violet. The protein crystals come out very 

 beautifully if the section is laid in a drop of 1 per cent, osmic 

 acid ; they gradually take on a brownish tint. Or an even better 

 result is obtained by first hardening the sections, and removing 

 the oil, by at least twenty-four hours in alcohol, then placing 



