BIBLIOGRAPHY — BIOLOGY. 343 



BIBLIOGRAPHY. 



Garrison, Fielding H., Army Medical Museum, Washington, District of 

 Columbia. Preparation and publication of the Index Medicus. (For 

 previous reports see Year Books Nos. 2-14.) 



The Index Medicus for 1915 contains 1,011 pages, 300 pages less 

 than the issue for 1914. The annual index of the same contains 170 

 pages, 45 pages less than that of the preceding year. The issue for 

 1914 contained 1,311 pages as against 1,448 pages for 1913. Thus, 

 in the period following the outbreak of the European War, there has 

 been a loss of some 437 pages of bibliographical material at the begin- 

 ning of 1916. Germany and Italy alone, of all the combatant coun- 

 tries, have kept up their quota of medical periodicals, but the German 

 periodicals have been difficult to obtain of late, under blockade con- 

 ditions, and for recent numbers the Index Medicus has been largely 

 indebted to the courtesy of the editor of the Journal of the American 

 Medical Association, and to the librarians of the New York Academy 

 of Medicine and the Boston Medical Library for loans. As soon as 

 the outstanding mass of foreign medical literature can be obtained, 

 it is proposed to print the titles in bulk as rapidly as possible, for the 

 sake of continuity and completeness. Through especial courtesy of 

 the Boston Medical Library, all the German periodicals up to March 

 1916 have been indexed, and this literature is contained in the double 

 number for the months of July-August 1916. 



BIOLOGY. 



Morgan, T. H., Columbia University, New York, New York. Study of the 

 constitution of the hereditary germ-plasm in relation to heredity. 



The work carried out by T. H. Morgan, A. H. Sturtevant, and C. B. 

 Bridges under the grant from the Carnegie Institution of Washington 

 has been concerned with the study of the chromosomes as furnishing 

 the mechanism of Mendelian heredity. More accurate data for the loca- 

 tion of about 30 factors already known have been obtained ; about 50 

 new mutant characters have been discovered, and about 40 of the factors 

 involved have been located in their chromosomes. These data, in con- 

 nection with data already on hand, give an opportunity for further 

 study as to the nature of linkage. This phenomenon of linkage is also 

 being more directly studied through variations caused (a) by environment 

 and (6) by genetic factors; (c) through interference and {d) through 

 non-disjunction and other unusual types of chi'omosome distribution. 



Besides the main lines of work enumerated above, experiments with 

 multiple factors and multiple allelomorphs are being carried out. These 

 studies have both a direct and an indirect bearing on the problem of 

 selection. This question of selection is being put to a crucial test, for 

 there is on hand material that is suitable to give a definite answer to 

 certain current speculations as to how selection accomplishes its results. 



