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McLeod and Govenlock (1) in 1921 reported the occurrence in pneumococcus cultures of a heat-labile substance which was inhibitory to the further growth of this and other organisms. The name bactericidin was first suggested by these authors. Further work by McLeod and Gordon (2,3) indicates that this substance is hydrogen peroxide, and that it may occur in cultures of organisms other than pneumococcus, as Bacillus bulgaricus, Bacillus acidophilus, and certain coccal and sarcinal forms. In a recent communication (4) these authors present a scheme of classification of bacteria based upon their properties of catalase production and sensitiveness to hydrogen peroxide.The growth-inhibitory substance of bacterial origin was found by the English investigators to be sensitive to the action of heat (85 0 C.), and of catalase; the gas evolved on adding catalase to a culture concentrate proved to be oxygen. From these and other chemical reactions they conclude that this unstable bactericidal product of growth which develops particularly in cultures of pneumococcus, is hydrogen peroxide rather than some organic peroxide. It does not occur in cultures deprived of oxygen or in those which contain abundant catalase. McLeod and Gordon further ascribe to the action of this substance the changes in blood pigment effected by growth of pneumococcus. They conclude that the early death of pneumococci in cultures is usually due to the accumulation of an excess of hydrogen peroxide.The present studies on bacterial peroxide, reported in this and subsequent papers, deal with the occurrence of this substance in cultures of pneumococci, its effect upon bacterial growth, and its relation to other phenomena of cell activity. The present paper is concerned with (1) the factors influencing the occurrence of peroxide in cultures of pneumococcus, (2) factors influencing the stability of 275 on

Penicillin has made the specific treatment of cardiovascular syphilis easy to give and easy to take and has all but abolished dangerous treatment reactions. Just as the curative therapy of acute syphilis with penicillin is simple and feasible, so is the prophylactic treatment of cardiovascular syphilis in individuals with latent syphilis and uncomplicated syphilitic aortitis simple and feasible. In spite of the fact that the effectiveness of such treatment has not been conclusively established, the prospects seem bright that the incidence of cardiovascular syphilis will decrease sharply in the immediate future. Cardiovascular syphilis may be treated, with or without preliminary bismuth and iodide "preparation," by the administration of 4.8 to 6 million units of penicillin in a period of 8 to 10 days. Larger doses and longer periods of treatment have been employed. Experience thus far does not indicate that penicillin therapy of established complications of syphilitic aortitis will be any more successful than was therapy of the pre-penicillin era.

In a previous paper on the immunological relationships of the cell constituents of Pneumococcus (1) two chemically distinct substances, namely the carbohydrate and protein of the cell, were shown to be intimately concerned in the serological specificity of this organism.The facts recorded at that time related only to the reactions exhibited by these substances in antipneumococcus serum prepared by immunization with the whole bacterial cell. In the absence of final evidence as to the antigenic properties of these two cell constituents the conclusions drawn were limited to their serological behavior. The observations made then have since been confirmed, and in the present report are extended to include the distinctive character of the isolated substances when each is tested for its function as antigen.

Peabody in 1912 (1) published a paper on the metabolism in pneumonia, in which he reviewed the previous literature and studied among other factors the blood gases and acid-base balance. Since Peabody, a number of other investigators have studied the blood gases and the question of the existence and importance of acidosis in pneumonia. The present paper is a report of observations on these subjects, in which recently developed methods have made possible the attainment of more complete results and apparently have justified the drawing of deductions more definite in some respects than those attainable from previous data.

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In previous papers it has been shown that unheated plant tissue, in the form of potato, contains the two factors necessary for the growth of organisms of the hemoglobinophilic group. Further studies (5) confirmed these findings and showed that yellow and white turnip, carrot, beet, parsnip, and sweet potato can replace blood in the cultivation of Bacillus influenzæ. In the present paper it has been shown that vegetable tissues also greatly facilitate and stimulate the growth of other organisms entirely unrelated to Bacillus influenzæ. Three varieties of Gram-positive cocci have been used in the present study, pneumococcus, Streptococcus hamolyticus, and Streptococcus viridans. With pneumococcus it has been previously shown that prompt and luxuriant growth will occur in broth containing unheated potato even though the seeding be so small that no growth whatever will occur with the same seeding in plain broth (5). In the present study it has been shown that even in dextrose broth this minimal inoculation is followed by a prolonged period of lag, whereas in potato broth this same inoculum serves to initiate immediate and rapid growth. When pneumococci are grown in potato broth not only is the period of lag abolished, but the stationary period of growth is extended and cell death is delayed. Moreover, in plant tissue medium the zone of hydrogen ion concentration within which growth of pneumococcus can be initiated is considerably extended beyond the acid and alkaline limits of the optimal range in ordinary bouillon. It has been found also that the presence of unheated plant tissue in the media likewise stimulates growth of hemolytic and non-hemolytic streptococci. In this investigation no attempt has been made to determine the exact nature of the substances in plant tissue upon which these properties depend. That they are not of the nature of readily fermentable carbohydrates, however, is made evident by the fact that no increased production of acid occurs in the pneumococcus culture when potato is present.

The known factors concerned in the autoinhibition of growth of pneumococcus are: 1. The accumulation of acid products of metabolism, resulting in unfavorable reaction changes in the medium. 2. The exhaustion of the nutritive substances of the medium. 3. Under certain cultural conditions the formation and accumulation of peroxide in the medium.