76 PHYSIOLOGY. 



this add i to 2 cc. of cobaltous nitrate soluti(jii (5 grams cobalt nitrate in too 

 cc. distilled water. Keep in a stoppered bottle), then add a small quantity 

 of a strong sodium hydrate solution (50 grams caustic soda, in sticks, to 

 100 cc. distilled water. Keep in a bottle). A beautiful violet color appears. 

 Test gluc(jse or grape sugar in the same way and a blue color appears, 

 whii h gradually changes to green. 



157c". Cane sugar (sucrose) can be changed to glucose or invert sugar 

 in the following way: To a weak solution of pure granulated cane sugar 

 in a small beaker add a few drojis of strong hydrochloric acid, rest on gauze 

 wire, and boil for a minute or two over a flame. This inverts the cane 

 sugar to glucose (equal parts of dextrose and la'vulose). To test for the 

 invert sugar the acid must be neutralized. Add sodium carbonate until on 

 adding no effervescence takes place. Now add the Fehling's solution and 

 boil; the red precipitate appears, showing that it reduces Fehling's solution. 

 158(1. Tests for sugar in plant tissue. — Si rajie out a little of the tissue 

 from the inside of a ripe apple ur pear, ]jlace it with a little water in a test 

 tube, and add a few drops of Fehling's solution. After standing half an 

 hour the characteristic precipitate of cc»ppjer and cuprous oxide appears, 

 showing that grape .sugar is present in quantity. 



Make thin sections of the apple and mount in a drop of Fehling's solution 

 on a slide. After an hour examine with the iui( roscope. The granules 

 of cuprous oxide are present in the cells of the tissue in great abundance. 



1586. Prepare another tube with some of the ]>ulp in 15 cc. of w"ater; 

 add 2 cc. of cobaltous nitrate solution, and then some of the strong sodium 

 hvdrate solution, as in paragraph 1576. Cane sugar as well as grape 

 sugar is present in these fruits. 



158c. Cut u]j se\'eral leaves of a vigorous young Indian corn seedling 

 in a small beaker and add 25 or 30 cc. distilled water. Boil for one or 

 two minutes. Filter. In another small lieaker boil Fehling's solution, 

 anfl if it is free fo^m sediment (if not, hlter) a<]d a portion of the liltered 

 corn-leaf solution anrl bnil fc.r two minutes. Hold the beaker toward the 

 light and look on the bottom for the red precipitate. Filter. The red 

 precipitate shows the presence of glucose (or in\ert sugar). Take the 

 remaining portion of the corn-leaf decoction in a test tube and test for cane 

 sugar by adding cobaltous nitrate and sodium hydrate as in jiaragrapli 

 1576. If the violet color does not appear al otuc, do not agitate it, bul 

 allow it to stand for a while. The violet . olor appears at the bottom of the 

 tube, showing the presence of cane sugar, while the reaction for glucose may 

 a]jpear in the U[)per portion of the solution. ['(.r comparison take similar 

 corn leaves, remove the chlorophyll with al. ohol, and test with iodine. Xo 

 starch reaction appears. The carbohydrate in 1 orii leaves is therefore sugar 

 and not starih. If now the grain of i nrn l.r cNamined the cells will be 

 found to be full of starch grains, which gi\e the beautiful blue reaction 



