ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 345 



From tlie foregoing considerations Molisch bases the following method 

 for demonstrating sugar in plant sections: — A not too thin section laid 

 on a slide is treated with a drop of 15-20 per cent, alcoholic a naphthol 

 solution, then two or three drops of concentrated HjSO^ are added. If the 

 section contains sugar the violet coloration appears in less than two minutes. 

 In other carbohydrates the colour appears in a quarter to half an hour. 

 In practice two sections are used ; one of these is boiled for a few minutes 

 in water, whereby sugar, dextrin, gum, and glucosides are dissolved. The 

 two sections are then submitted to the same test, and if sugar is present 

 in the unboiled section the coloration immediately appears. As dextrin, 

 gum, and glucosides may be usually disregarded, the appearance of the 

 violet, &c., staining indicates with great probability the presence of sugar. 



The foregoing test may be used to demonstrate the presence of inulin, 

 which by Sachs's method is liable to be confounded with sphgero-crystals, 

 for these become immediately stained deep violet with a naphthol and 

 sulphuric acid, and on tlie addition of thymol are dissolved with the 

 production of a red colour. 



These reactions may be used for the detection of sugar in urine. 

 Without any preparation normal human urine exhibits them distinctly, 

 even when it is diluted from 100 to 300 times; and the presence of 

 grape-sugar is therefore absolutely determined in the urine of man in a 

 normal condition. A simple method, based on these reactions, is given 

 for the distinction of diabetic from normal urine. 



Discriminatioii of Butter and Fats. — Prof. H. A. Weber * has made 

 further experiments upon the microscopic methods of distinguishing butter 

 from other fats proposed by Dr. T. Taylor, f 



Dr. Taylor's first claim was that butter, cooled slowly under certain 

 conditions, formed " globules," which, when viewed by polarized light, 

 showed a well-defined St. Andrew's cross. Prof. Weber having shown that 

 this appearance was not characteristic of genuine butter, but might be 

 produced in any common fat by treatment similar to that applied to the 

 butter. Dr. Taylor then called attention to another test as being charac- 

 teristic. According to this, if a sample of butter is viewed by polarized 

 light, a plain selenite being placed between polarizer and analyser, a 

 uniform colour is observed ; if any solid fat, like lard or tallow, be thus 

 viewed, the fat will exhibit prismatic colours. Prof. Weber finds this test 

 as fallacious as the former. Any of the fats under consideration, if melted, 

 and cooled slowly, and then submitted to Dr. Taylor's test, will show the 

 prismatic colours, due to the action of the comparatively large crystals 

 formed upon the polarized light. On the other hand, the same fats, if 

 cooled quickly, so as to prevent the formation of large crystals, present the 

 uniform tint claimed by Dr. Taylor as characteristic of butter fat. 



Dr. Taylor in reply contends X that Prof. Weber's experiments were 

 erroneously carried out, and his views are defended against those of Prof. 

 Weber by Mr. R. Hitchcock. § Mr. C. M. Vorce also corroborates |1 Dr. 

 Taylor, and describes a modified method of his own. 



Dr. J. H. Long, If on the other hand, considers that wo have no abso- 



* Science, vii. (1886) p. 524, from Bulletin No. 15 Ohio Agricultural Experiment- 

 Station. 



t See this Journal, 1885, pp. 356 and 918. It would seem from the above that 

 these two extracts, though given in the order of date of tlie sources from which they 

 "were taken, -were chronologically reversed. See also this Journal, 1886, p. 174. 



X The Microscope, vi. (1885) pp. 7b-9, and see pp. 85-6. Amer. Mon. Micr. Journ., 

 vii. (1886) pp. 169-70. 



§ Amer. Mon. Micr. Journ., vii. (1886) pp. 119, 135-7. || Ibid., pp. 156-7. 



1 Bull. Illinois State Micr. Soc, May 14, 1886, 5 pp. and 1 pi. 

 1887. 2 A 



