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SCIENCE 



[N. S Vol. XLII. No. 1078 



limited to national interests or whose point of 

 view is purely economic have not discovered it. 

 Pacifist, eugenist and feminist all miss it. 

 Eather is it known only by those "who are 

 beginning to perceive that the social problem 

 is now what it has been in all ages, namely 

 the problem of the relations of men to one an- 

 other." These relations are the outcome of 

 concrete historical, physical, physiological, 

 economic and ideal elements. For example, on 

 the historical side the relations of men in 

 western civilization are largely determined by 

 inheritance of Greek, Hebrew, Roman and 

 Teutonic customs and ideals. Briefly attempt- 

 ing to characterize some of the chief contribu- 

 tions of each of these factors, the author en- 

 deavors to show how various inharmonious 

 elements in them have combined with specified 

 unfortunate effects of physical and economic 

 influences to produce undesirable conditions in 

 present society. A final chapter, on " The Solu- 

 tion of the Social Problem," lays down a 

 number of precepts. To " solve " the social 

 problem we must take a synthetic view of our 

 social life, avoid revolution and violence, 

 develop sympathy among all classes in the 

 population, advance education, purify family 

 life, control heredity, inculcate social respon- 

 sibility, stress reason and altruism, support 

 science, readjust the economic system and 

 finally as a means to all this find and train 

 social leaders. 



In covering so large a field in so short a 

 volume Professor Ellwood has necessarily dealt 

 in cavalier fashion with most of his topics. In 

 consequence the cautious scientist who looks 

 in this book for adequate proof of all positions 

 taken will be disappointed. The discerning 

 reader, nevertheless, may possibly draw the not- 

 unscientific conclusion from it that the world 

 is still full of a number of things that need 

 careful investigation. It is to be feared, how- 

 ever, that not all into whose hands " The 

 Social Problem " falls will be able to distin- 

 guish opinions from generalizations that have 

 been established through the work of numer- 

 ous investigators. 



A. A. Tennet 



Columbia University 



SPECIAL ARTICLES 



NEW METHODS IN SOIL PROTOZOOLOGY^ 



In the investigation of a problem bearing 

 on the conclusions of Russell and Hutchinson^ 

 who consider protozoa as one of the limiting 

 factors of bacterial activity and consequently 

 of soil fertility, the authors found it expedi- 

 ent to carry on several preliminary experi- 

 ments for the purpose of establishing the value 

 of certain newly devised methods. 



In view of the fact that the methods em- 

 ployed for counting protozoa have been un- 

 satisfactory even in the hands of such ex- 

 perienced investigators as Rahn,^ using 

 an application of the bacterial dilution 

 method; Killer* plating on solid media; Miil- 

 ler' counting protozoa per standard loopful of 

 solution; and numerous others counting the 

 protozoa directly in a drop by means of a 

 microscope ; the authors have adapted the well- 

 known blood-counting apparatus (Blutkorper- 

 z'ahlapparat) to the counting of protozoa. The 

 principle underlying the use of this instru- 

 ment is the microscopical observation of a 

 drop of standard size. The organisms may be 

 examined in the stained or unstained, in the 

 living or dead state. Picrosulphuric acid 

 (Kleinenberg) is recommended for killing and 

 rapid staining simultaneously. 



The calculation of results is based on the 

 use of a standard stage micrometer, the 

 squares marked on the disc of the slide, and 

 the constant depth of solution under observa- 

 tion, which is .1 mm. Thus no mechanical 

 variation is possible. The advantages of using 

 this apparatus for counting protozoa are as 

 follows : 



1. It is a direct method, thus eliminating 

 many errors attending incubation, etc., and the 

 results can be reported immediately. 



1 From the laboratories of Protozoology and Soil 

 Bacteriology. Further results of experimentation 

 and a bibliography on soil protozoology and soil 

 sterilization are awaiting publication in coming 

 issue of Centr. f. Bakt., Abt. II. 



- Eussell and Hutchinson, Jour. Agr. Sci., 3 

 (1909), 111; ihid., 5 (1913), 152, etc. 



sRahn, 0., Centr. f. Bakt., II., 36 (1913), 419. 



4 Killer, Centr. f. Bakt., II., 37 (1913), 321. 



sMiiller, Archiv. f. Byg., 75 (1912), 321. 



