778 EXPERIMENT STATION RECORD. [Vol.41 



to assume that the degree of i-esponse is proportional to the logarithm of the 

 stimulus, and to the tissue reactivity. The stinmlating power of an organism 

 (or its products) probably depends upou its degree of saturation (sensitiza- 

 tion)." 



On the basis of this theory a system of classification of diseases due to or- 

 ganismal invasion on the one hand and influences acting in a contrary manner 

 on the other is outlined, in which the main clinical types of diseases fall into a 

 broken series. At the two extremes of this series stand diseases like pneu- 

 monia, in which protective efforts are in excess, and chronic infection in which 

 protective efforts are continually overbalanced. Malta ievev, representing a 

 type of relapsing disease, lies near the neutral point in this scheme, where the 

 balance betweea protective efforts and opposing influences is exact. 



The effect of feeding yeast on antibody productions, E. P, Wolf and J. H. 

 Lewis (Jour. Infect. Diseases, 25 {1919), No. 4, pp. 311-314). — With a view to a 

 possible explanation of the therapeutic value claimed for yeast in infectious 

 diseases, the effect of the feeding of yeast on the production of antibodies to 

 sheep blood cells in rabbits was studied. 



From the results obtained, the authors- conclude that yeast does not act by 

 Increasing antibody formation in the rabbit. On the contrary, it may even 

 cause a reduction in the amount of antibodies formed as compared with those 

 of the control animals. Yeast was also found to be lacking in the laxative value. 



Hydrogen-ion concentration of cultures of pneumococci of the different 

 types in carbohydrate media, O. T. Avery and G. E. Cullen (Joia: Expt. 

 Med., 30 (1919), No. 4, pp. 359-318, figs. 2).— This paper reports a study of the 

 H-ion concentration of cultures of pneumococcus in carbohydrate media under 

 different conditions, the results of which may be summarized as follows : 



The optimum H-ion concentration for the growth of pneumococcus is pH 7.8. 

 If sufficient fermentable carbohydrate (above 0.4 per cent) is present in broth 

 cultures of pneumococcus, growth continues until a final H-ion concentration of 

 about pH 5 is reached, but if less carbohydrate is present growth ceases at a 

 lower H-ion concentration. If no carbohydrate is present except that extracted 

 from the meat of which the broth is made, growth initiated at pH 7.8 ceases at 

 about pH 7. 



If bacteria-free filtrates of plain broth cultures in which growth has ceased 

 are readjusted to pH 7.8 and reinoculated with pneumococcus, no growth occurs 

 mdess carbohydrate is added, but a similar readjustment of bacteria-free fil- 

 trates of dextrose broth cultures causes growth. 



All of the carbohydrates which were fermentable under the conditions used 

 gave the same results in, the rate of reaction change and final H-ion concentra- 

 tion attained, and the different immunological types of pneumococcus behaved 

 alike in fermenting these carbohydrates. 



The pathogenicity of Bacterium melitensis for guinea pigs, K. F. Meyeb, 

 E. C. Fleischner, and E. B. Shaw {Troc. Soc. Expt. Biol, and Med., 16 (1919), 

 No. 8, pp. 152-156). — The authors confirm the relationship of Bacillus abortus 

 to B. melitensis previously demonstrated by Evans (E. S. R., 89, p. 289), and 

 announce two additional characteristics of similarity as follows: 



(1) Guinea pigs infected with B. abortus developed striking reactions of 

 cutaneous hjiiersensitivenoss with melitensis protein, and in animals success- 

 fully infected with B. melitensis skin reactions were obtained with aborto- 

 protein. (2) By intratesticular injection in guinea pigs of a one-tenth agar 

 slant of strains of B. melitensis, a disease Was produced with pathological 

 changes which could not be distinguished from those seen in guinea pigs suffer- 

 ing from abortion disease. The lesions of two guinea pigs were diagnosed 

 definitely to be the result of a B. melitensis infection only by cross agglutina- 

 tion and absonition with the recovered bacteria. 



