688 



SCIENCE 



[N. S. Vol. XLI. No. 1062 



high, high, fair, low and very low; and under 

 I, GV and 8, very dark, dark, fair, light and 

 very light." 



The procedure in the examination of the 

 several starches by Dr. Eeichert is as follows : 

 The temperature of gelatinization and inten- 

 sity of color of aniline dyes was determined by 

 placing a small amount of starch in a test 

 tube containing in the one case 10 c.c. or an 

 excess of water and in the other case 5 c.c. 

 or an excess of solution of the dye. In using 

 iodine solution he does not say how much 

 starch was employed, but merely states that 

 "the starch was placed on a slide and one or 

 two or more drops of the iodine solution added, 

 the whole covered with a cover slip." In the use 

 of swelling reagents we read that " a small 

 amount of starch is placed on a slide, several 

 drops of the reagent added, a cover glass put 

 on, and the progress of events examined under 

 the microscope." Granting that there is a 

 certain variation to a limited extent in the 

 shade and intensity of color produced by cer- 

 tain reagents with some of the starches,^ these 

 differences will only hold when definite quan- 

 tities of starch and definite quantities of re- 

 agent are used. From the statements in the 

 foregoing paragraph showing the method of 

 making microscopic mounts, it is apparent 

 that Dr. Eeichert did not bear in mind this 

 fundamental fact as he did not use definite 

 quantities of starch with definite quantities 

 of reagent. One illustration is sufficient to 

 show the weakness of his technique and the 

 untrustworthiness of his results. Let the 

 worker make four mounts, using varying quan- 

 tities of starch and iodine solutions as follows : 

 (1) 0.003 gm. of starch and 1 drop of iodine 

 solution; (2) 0.006 gm. of starch and 1 drop of 

 iodine solution; (3) 0.003 gm. of starch and 

 2 drops of iodine solution; (4) 0.006 gm. of 

 starch and 2 drops of iodine solution. If a 

 solution be employed containing 0.25 per cent, 

 of Lugol's solution as adopted by Dr. Eeichert, 

 the intensity of color will not be as pronounced 

 as if a reagent containing 0.50 per cent, of 

 Lugol's solution be used. In any case the re- 

 actions in the several mounts will show con- 



iBot. Gae., October, 1905. 



siderable variation, a more intense blue colora- 

 tion being usually discernible in mounts con- 

 taining 0.003 gm. of starch and 2 drops of 

 reagent and weakest in mounts containing 

 0.006 gm. of starch and 1 drop of reagent. 

 Nearly equally as striking differences will be 

 obtained when using varying quantities of 

 starch with two or more drops of the swelling 

 reagents employed by Dr. Eeichert. A more 

 noticeable and complete swelling • being pro- 

 duced when less starch (0.006 gm.) is em- 

 ployed, with an excess of reagent (4 drops), 

 and a partial or incomplete gelatinization al- 

 ways being observable when an excess of starch 

 (0.012 gm.) are used with a minimum quan- 

 tity (2 drops) of the swelling agent. When we 

 consider the nature of starch these varying 

 results are to be expected unless a quantita- 

 tive relation be borne in mind between the 

 amount of starch and the number of drops of 

 reagent employed. 



The method employed by Dr. Eeichert in 

 determining the temperature of gelatinization 

 and of coloration with aniline dyes might have 

 been applied to the use of other reagents. In 

 the designation of intensity of color reaction 

 with aniline dyes and iodine, Dr. Eeichert 

 was unfortunate in adopting an arbitrary scale 

 of very dark, dark, fair, light and very light, as 

 hardly any two observers would agree as to 

 whether a color was dark or fair, etc. It 

 would have been a great deal better had there 

 been an accurate color scale embodied in the 

 publication so that Dr. Eeichert's work could 

 be confirmed. 



In view of these serious criticisms involving 

 a crude technique and one which is liable to 

 give discordant results in the hands of different 

 investigators we must conclude that Eeichert's 

 work has added practically nothing to the inter- 

 esting question of stereoisomerism of the 

 starches, nor can it be considered as a serious 

 contribution to our knowledge of the specific- 

 ity of starches in relation to genera, species, 

 etc. Apparently it will be very difficult for 

 any one very soon to add anything of a funda- 

 mental character or in a comprehensive way 

 to the study of starches and that can be at all 

 compared to the monumental work on "Die 



