August 17, 1917] 



SCIENCE 



167 



trons from Welinelt cathodes is due to a sim- 

 ilar mechanism to that causing the emission 

 from heated pure metals. 



Daily variations of water and dry matter 

 in the leaves of corn and the sorghums: 

 Edwin C. Miller, Kansas Agricultural Ex- 

 periment Station. Under the conditions of 

 these experiments the sorghiuns, and more 

 particularly milo, absorb water from the soil 

 and transport it to the leaves more rapidly in 

 proportion to the loss of water from the plant 

 than does corn; and thus the sorghums can 

 produce more dry matter for each unit of leaf 

 area under severe climatic conditions than 

 can the com plant. 



Note on complementary fresnellian fringes: 

 Carl Barus, Department of Physics, Brown 

 University. 



The displacement interferometry of long 

 distances: Carl Barus, Department of Phys- 

 ics, Brown University. In preceding notes 

 two methods for measuring small angles have 

 been suggested. Application is here made to 

 the determination of distances and is shown 

 that an object at about a mile should be 

 located to about thirty feet. 



National Research Council: Meetings of the 

 Executive Committeee and the Joint Meeting 

 of the Executive, Military, and Engineering 

 Committees. Eeport of the Astronomy Com- 

 mittee. Ed\\in Bidwell Wilson 



Mass. Institute of Technology, 

 Cambridge, Mass. 



SPECIAL ARTICLES 

 INTRA-VITAM COLOR REACTIONS 



We have slowly come to have great confi- 

 dence in the specificity of certain physiological 

 actions. We introduce into an organism cer- 

 tain substances, and definite results follow; but 

 about the only thing we know in the matter is 

 that the results follow with certainty. In such 

 eases, if only we could see what it is that hap- 

 pens while it is happening, it seems certain 

 that important advances would be made in our 

 knowledge of nutrition, growth and decay — 

 of physiology, pathology and medicine. 



If substances giving color reactions in liv- 

 ing tissues could be applied to small, trans- 

 parent, varied and highly complex living or- 



ganisms, under circumstances that would per- 

 mit microscopic examination while the reac- 

 tions are in progress, we might hope for more 

 light on this exceedingly important subject. 

 Experiments I have made lead to the belief 

 that many of the conditions requisite for suc- 

 cess in this line of investigation can be much 

 more fully realized than hitherto by feeding 

 colored substances, notably coal-tar dyes, to 

 free-living nematodes. 



These minute, transparent animals are com- 

 paratively highly organized ; not only this, but 

 also extremely varied in their mode of life. 

 Some are exclusively vegetarian, others ex- 

 clusively carnivorous, and others omnivorous. 

 They constitute a group composed probably of 

 hundreds of thousands of species, embodying 

 an almost inconceivable number of kinds of 

 physiological action. Their organs are en- 

 closed in a thin transparent cuticle, and are 

 strung out so as to make them unusually suit- 

 able for intra-vitam examination. Under 

 slight pressure the nema flattens out more or 

 less without losing its vitality sufficiently to 

 preclude satisfactory intra-vitam examination 

 under the highest powers of the microscope. 



Observing certain precautions, I find that a 

 gnat variety of coal-tar compounds and other 

 colored compounds can be fed to nemas, ap- 

 parently without interfering materially with 

 their normal metabolism. I have had the best 

 results by cumulative action, using small quan- 

 tities of color dissolved in the medium in 

 which the nema lived, and allowing the dye to 

 act for days or weeks. 



Not infrequently the dyes prove to be highly 

 specific in their action. Only certain cells, or 

 only definite parts of certain cells, exhibit vis- 

 ible reactions in the form of colorations. The 

 results obtained by the use of any given dye 

 may be quite varied. It is evident in many 

 cases that the dye is digested and assimilated, 

 thereby undergoing molecular changes by 

 which it is converted into new compounds in a 

 manner analogous to the processes exemplified 

 in chemical laboratories devoted to the produc- 

 tion of aniline dyes. Thus, a dye may give 

 rise to several different colors, none of them 

 like that of the dye itself, and all of them very 



