112 EXPERIMENT STATION EECORD. 



bonate. The same fermentation can be produeetl with the potassium salt of 

 oxalacetic acid. 



The biological analysis of casein antiserum, A. Klein (Folia Microbiol. 

 [DelfO, 1 {1912), No. 1-2, pp. 101-162, table 1; abs. in Milchw. Zentbh, 41 

 {1912), No. 23, pp. 720, 721). — The antiserum used in these investigations was 

 prepared by injecting casein solutions into rabbits. It was invariably found 

 that 2 kinds of precipitins were produced, which had the following distinguish- 

 ing features: 



Calcium casein precipitin acts exclusively in the presence of calcium chlorld 

 with an optimum activity at a concentration of 5 parts per thousand. Casein 

 precipitation is the most complete when calcium chlorid is absent, and the pre- 

 cipitation decreases as the calcium chlorid increases. Calcium casein precipitin 

 shows an optimum activity with 2 mg. of casein, and casein precipitin with 0.1 

 mg. of casein. Both of the precipitins are weakened by diluting the serum with 

 physiological salt solution, or by adding an alkali, but casein precipitin is the 

 more affected. The addition of water to fresh antisera produces a precipitate 

 in casein sera, but not in calcium casein sera. As the antisera grow older, or 

 are heated to 55° C, casein precipitin loses some of its precipitating capacity ; 

 no such effect is noted with calcium casein precipitin. In the process of im- 

 munizing, calcium casein precipitin first makes its appearance in the sera. The 

 calcium casein precipitation reaction obtained w'ith the casein antisera and 

 lactosera does not detect more than ±1/30 mg. of casein. Casein precipitins do 

 not detect more than 1/100 mg. casein, and in this respect resemble glycerin- 

 acetic acid. Casein precipitin also inhibits the action of calcium casein anti- 

 serum. 



Some applications of lacto- and ovosera, B. Galli-Valekio and M. Born and 

 {Ztschr. Immumtdtsf. u. Expt. Ther., I, Orig., IJf {1912), No. 1, pp. 32-1,1, fig. 1; 

 abs. in Gentbl. Bakt. [etc.^, 1. Abt., Ref., 55 {1912), No. 8, p. 233).— With a 

 lactoantiserum it was possible to detect casein, particularly in feces and in 

 fats. Likewise it was possible with a fowl antiserum to detect eggs in various 

 foodstuffs. 



A contribution to our methods of determining" nitrogen in humus, C. B. 

 I.iPMAN and H. F. Pressey {Jour. Indus, and Engin. Chem., 5 {1913), No. 2, 

 pp. 143, 144)- — While much work has been done in regard to methods for 

 determining humus in soils, very little appears to have been reported with 

 reference to the determination of nitrogen in the humus. To obtain a more 

 uniform and reliable method for determining nitrogen, the Wilfarth. Gunning- 

 Atterberg, Hibbard, and salicylic acid methods were compared. The soils from 

 which the humus solutions were obtained included light sandy soil from a 

 walnut orchard, Anaheim, Cal., with a humus content of 0.55 per cent; silty 

 clay loam derived from the State of Washington, humus content 8.89 per cent ; 

 and tule soil from an island in the Sacramento River, nearly all organic matter. 

 humus content 28.7 per cent. 



The Hibbard method gave the highest amounts of nitrogen in all cases except 

 one, thus showing a more thorough digestion, and its duplicate and triplicate 

 determinations showed the best agreement. The digestion was carried out 

 more rapidly than in any other method, and particularly than by the salicylic 

 acid method which, in other respects, came the nearest to the Hibbard method 

 in yielding satisfactory results. Considerable trouble with bumping was ex- 

 perienced with all methods except the Hibbard, in which the digestion proceeded 

 rapidly and quietly in all cases. Its manipulation also surpassed in simplicity 

 and speed all the other methods tested. " In view of the fact, therefore, that the 

 Hibbard method is far superior to the others so far as both accuracy and 

 speed are concerned, its use is urged in all humus nitrogen determinations." 



