Mr. Paterson on the Yam. 31 



lent quality, I was indebted to Dr. R. D. Thomson. The experiments 

 were conducted in the College laboratory under his superintendence. 



Half a pound avoirdupois of yam was taken, after being deprived of 

 all extraneous matter and skin, and was carefully rasped down and 

 allowed to fall into a clean porcelain basin, previously weighed. The 

 yam and basin were again weighed. The pulp was then thrown on a 

 scarce, and washed with distilled water till it passed through clear ; the 

 residue was then triturated and filtered, which diminished its bulk con- 

 siderably. 



On being tested by iodine, the starchy reaction was strongly marked. 

 It was further subjected to a second trituration, and washed, when it still 

 indicated the presence of starch, but in a much more faint degree. 



The ultimate residue was then collected from the scarce, dried at 

 212°, and weighed. It was then a hard, gray, woody looking substance, 

 and had a faint resemblance to crumbs of very hard coarse sea biscuit, 

 and was fibrous ligneous matter, and contained a mere trace of nitrogen, as 

 was ascertained by experiment. 



The solution, and that portion of the pulp which passed through the 

 scarce, was filtered through a weighed calico filter, and washed till the 

 water passed through clear ; what remained on the cloth was dried at 

 212°, and weighed ; it was white and granulated, gelatinised when boiling 

 water was added, and gave a bright blue with iodine. 



The solution was then evaporated, and on being heated to the boiling 

 point, a portion coagulated, being vegetable albumen, and on the addition 

 of a little acetic acid, the quantity was greatly increased, the increase 

 being vegetable casein. After being coagulated thoroughly, it was 

 filtered and washed with difficulty, dried at 212°, and weighed. Colour 

 dark gray. 



The solution was then evaporated, and became a thick gummy sub- 

 stance ; it was finally dried at 212° and weighed. It was then boiled 

 for a length of time in water, to which some sulphuric acid was added, 

 the water being replaced as it evaporated. As much chalk was then 

 added as neutralized it. It was then filtered, and the solution evaporated, 

 when there remained sugar, but having a brackish taste. 



Specific gravity of yam employed was ri416. It contained 77"81 of 

 water, 2r2G organic matter, and 0-93 of ash. By the above analysis, 

 it gave, — 



Fibrous ligneous matter, 8-51 



Starch, 15-02 



Casein, 2'25 



Sugar and Gum, 0'73 



Soluble salts, 0-75 



Insoluble salts, 0"18 



Water, 77*81 



100-07 



