220 



SCIENCE 



[N. S. Vol. XLVII. No. 1209 



ing, dehydrating and clearing processes in ordi- 

 nary mieroteclinique, especially when objects 

 and stages of diverse nature are to be passed 

 througli in large numbers at a time. Hig- 

 gins's waterproof ink and preparations involv- 

 ing sodium silicate either wash off, or, if they 

 survive to the end, rub off when dry in spite of 

 even the most careful handling. West, in a 

 recent number of Soience,i suggests the use 

 of numbered aluminum clips and a notebook. 

 This method would appear to be clumsy and 

 wasteful of time and imperfectly adapted to 

 slides of varying thickness, besides necessi- 

 tating permanent labeling of the slides as 

 soon as the small supply of clips becomes ex- 

 hausted. To meet these objections, an ink has 

 been devised which apparently answers all 

 ordinary requirements of the investigator. It 

 has been used in the making of hundreds of 

 slides, and one supply made two years ago is 

 still giving great satisfaction. 



The method of making the ink may be 

 stated briefly as follows : 15 g. of best cabinet- 

 makers' glue are dissolved at low temperature 

 in 100 c.c. of water in a clear glass bottle. To 

 this is added an excess of crystals of potassium 

 dichromate and the mixture is exposed for a 

 week or more to strong light, after which it is 

 filtered. India ink is rubbed into this " stock 

 solution," a slate ink cup or grinder being 

 employed. A little of the solution is poured 

 into the cup and a stick of India ink is ap- 

 plied, the rubbing being done with a circular 

 motion. When sufficient blackness is obtained, 

 the ink is removed with a dropper to a small 

 bottle; the operation is repeated with a new 

 supply of stock solution until a sufficient quan- 

 tity of ink is accumulated. A supply sufficient 

 for several years' use can be made in this way 

 in the course of an hour or two. 



The ink will keep indefinitely if care is 

 taken to prevent evaporation. It may best be 

 kept in a small narrow-neck balsam bottle 

 with ground joint, the joint being further 

 sealed with a thin coating of vaseline. The 

 label end of the slide should be clean and free 

 from fixative, when the ink wiU flow freely. 



1 N. S., Vol. XL VII., No. 1201, January 4, 1918, 

 p. 22. 



An ordinary clean, medium-pointed steel pen 

 may be used. A dozen slides may be labeled 

 with accession number, thickness of ribbon 

 and other data with a single dipping of the 

 pen. The ink will dry thoroughly in a few 

 minutes at ordinary room temperature, after 

 which the slides may be passed through the 

 alcohols, stains, water and xylol without de- 

 terioration of the label. On completion of the 

 slides the label may be left as originally made 

 and the slides stored in this condition until 

 they are wanted. This will be found sufficient 

 for most research problems. If it is desired at 

 any time to replace the original label with a 

 permanent one, the ink may be quickly 

 scraped off with a scalpel and replaced by a 

 pasted label. In doing this the figure or letter 

 usually comes off entire with a slight lifting 

 movement of the knife. 



Chas. H. Otis 

 Biological Laboratory, 

 Western Reserve UNrraRSirr, 

 Cleveland, Ohio 



professional courtesy 

 In the January, 1918, number of the Journal 

 of Biological Chemistry appeared an article by 

 E. V. McCoUum and N. Simmonds, now of 

 Johns Hopkins University, entitled " A Study 

 of the Dietary Essential, Water-Soluble B, in 

 Relation to Its Solubility and Stability To- 

 wards Reagents." 



This work, as the article indicates, was done, 

 but not prepared for publication, in the labora- 

 tory of agricultural chemistry of the Uni- 

 versity of Wisconsin. The authorship of this 

 article does not properly give credit to those 

 participating in this research. On page 62 

 a footnote briefiy states that " Credit is due 

 Mr. H. Steenbock for the preparation of the 

 extracts employed in this work." This repre- 

 sentation is a gross injustice to Professor 

 Steenbock and displays a marked transgression 

 of common professional courtesy and ethical 

 standards on the part of the authors of this 

 article. Professor Steenbock not only contrib- 

 uted much, if not all, to the thought expressed 

 in the preamble of this article, but the details 

 of making the vitamine preparations and the 



