SOLUTION AND FIXATION OF BIOCOLLOIDS 



133 



came down to a thickness of about 0.2 nun. and these gave 

 swellings at 16°C. as below: 



The dried median slices show a general behavior similar to that 

 of the epidermal slices of the first species, the most important 

 feature being the difference between the first and second swell- 

 ings. These are very marked and indicate the extraction of 

 some substance which gives a high coefficient of swelling. 



The solution of material from a section of a plant with its 

 thousands of cellulose walls presents physical features that are 

 not easily to be duplicated. Ammo-acids, hexoses, malates, and 

 salts however constitute the bulk of the extracted material, 

 together with other substances set frejs by the bursting w T alls of 

 some of the cells, in addition to those crushed in taking out the 

 section. Diffusion of the pentosans would take place slowly, 

 although the derivation of large proportions of this material by 

 extraction after killing with ether suggests that the rate is not 

 inconsiderable, and may be subject to various modifications. 



The lessened hydration capacity of a section previously 

 extracted is probably a resultant of various losses. The salts 

 would operate to limit imbibition of a carbohydrate-protein 

 colloid and their extraction would remove this limit. Free 

 acids limit swelling. Extraction may remove acids and salts 

 which lessen swelling, and at the same time some amino- 

 compounds which give to pentosans a high hydration capacity. 

 The second swelling therefore represents a series of reactions 

 widely different from those of the first treatment. 



It was not practicable to make determinations of the ex- 

 traction of material in all the solutions but attention was given 



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