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POPULAR SCIENCE MONTHLY. 



and his associates feel justified in the 

 following conclusion: "The mosquito 

 serves as the intermediate host for the 

 parasite of yellow fever, and it is highly 

 probable that the disease is only prop- 

 agated through the bite of this insect." 



One of the most obscure points in 

 chemistry is the action of ferments. 

 These have been grouped in two classes : 

 Organized ferments like the yeast plant, 

 or the mycoderma aceti, which oxidize 

 alcohol to acetic acid; and the unorgan- 

 ized ferments, like diastase, which con- 

 vert starch into sugar. In both cases 

 a very small quantity of the ferment is 

 capable of converting an indefinitely 

 large amount of the fermenting sub- 

 stance into the fermented product, al- 

 though the ferment itself does not enter 

 as such into the reaction. Further, the 

 action of ferments can be inhibited by 

 heat and by the action of certain sub- 

 stances which act as poisons. Recent 

 investigations seem to show that the or- 

 ganized ferments may owe their action 

 to unorganized ferments which they se- 

 crete. More recently attention has been 

 called by Bredig and von Berneck to 

 the similarity between the action of fer- 

 ments, and what has been called con- 

 tact action of metals. For example, fine- 

 ly divided platinum can oxidize alcohol 

 to acetic acid, and can invert cane sugar. 

 Much more marked is the action of a 

 solution of colloidal platinum, obtained 

 by passing a strong current of electric- 

 ity between platinum poles under water. 

 The action of the platinum in this con- 

 dition is remarkably like that of a fer- 

 ment. When its effect upon hydrogen 

 peroxide was studied it was found that 

 one part in about 350,000,000 parts of 

 water was sufficient to decompose hydro- 

 gen peroxide appreciably. Minute traces 

 of certain poisons affect the reaction 

 strongly; especially is this true of prus- 

 sic acid, hydrogen sulfid and corrosive 

 sublimate. Like many ferments the plat- 

 inum solution gradually recovers from 

 the poisonous effects of traces of potas- 

 sium cyanid. It also appears that the 

 platinum plays no chemical part in the 



reaction, and thus it is apparently a true 

 ferment. It seems probable that the 

 study of these inorganic ferments may 

 throw much light upon the action of 

 the very complicated organic ferments. 



When the discovery was made some 

 ten years ago that leguminous plants 

 are able to assimilate the free nitrogen 

 of the atmosphere, and thus to supply 

 themselves with one of the necessary 

 elements of plant food, its importance to 

 agriculture as an economical means of 

 maintaining soil fertility was recognized 

 almost immediately. In working out 

 the practical application of the discov- 

 ery it was found that the micro-organ- 

 isms which effect this nitrogen assimi- 

 lation are not the same for all kinds of 

 legumes, but that different kinds have 

 their specific organisms, and further- 

 more that these micro-organisms are 

 not universally disseminated through 

 the soil. This led to inoculation of the 

 soil, either with pure cultures of the 

 specific bacteria or with soil from a 

 field known to contain them in abun- 

 dance. What seemed so simple theoret- 

 ically has been found in practice to be 

 only partially successful, so that the 

 progress in its application has been 

 somewhat delayed. A very interesting 

 account of experiments in inoculating 

 soils for the growth of the soy bean 

 has recently been published by the Kan- 

 sas Experiment Station as Bulletin No. 

 96. It is one of the most successful at- 

 tempts at soil inoculation on a large 

 scale that has been reported in this 

 country or in Europe, where this 

 method for promoting nitrogen assimi- 

 lation was first suggested. It- was 

 found that the Kansas soil contained 

 none of the organisms necessary for the 

 soy bean, and that in such soil the roots 

 produced none of the tubercles which 

 are intimately associated with nitrogen 

 assimilation. A quantity of soil was 

 obtained from the Massachusetts Ex- 

 periment Station, where the soy bean 

 had been grown for several years, and 

 mixed in very small proportion with 

 the Kansas soil, with the result that 



