Toxin of sufficient strength to kill a 400-gramme guinea-pig in three days and a half in a dose of 0·cubic centimetre developed in suitable bouillon, contained in ordinary Erlenmeyer flasks, within a period of twenty-four hours. In such boullon the toxin reached its greatest strength in from four to seven days (0·005 cubic centimetre killing a 500-gramme guinea-pig in three days). This period of time covered that of the greatest growth of the bacilli, as shown both by the appearance of the culture and by the number of colonies developing an agar plates. The bodies of the diphtheria bacili did not at any time contain toxin in cosiderable amounts. The type of growth of the bacili and the rapidity and extent of the production of toxin depended more on the reaction of the bouillon than upon any other single factor. The best results were obtained in bouillon which, after being neutralized to litmus, had about seven cubic centimetres of normal soda solution added to each litre. An excessive amount of either acid or alkali prevented the development of toxin. Strong toxin was produced in bouillon containing peptone ranging from one to ten per cent. The strength of toxin averaged greater in the two and four-per-cent peptone solutions than in the one-percent. When the stage of acid reaction was brief and the degree of acidity probably slight, strong toxin developed while the culture bouillon was still acid; but when the stage of acid reaction was prolonged, little if any toxin was produced until just before the fluid became alkaline. Glucose is deleterious to the growth of the diphtheria bacillus and to the production of toxin when it is present in sufficient amounts to cause by its disintegration too great a degree of acidity in the fluid culture. When the acid resulting from decomposition of glucose is neutralized by the addition of alkali the diphtheria bacilus again grows abundantly. Glucose is not present, at least as a rule, in sufficient amounts in the meat as obtained from the New York butchers to prevent the rapid production of strong toxin if the bouillon is made sufficiently alkaline. In our experiments, when other conditions were similar, the strength of the toxin was in proportion to the virulence and vigour of growth of the bacillus employed.

1. Typical pneumococci were present dunng the winter months in the throat secretions of a large percentage of healthy individuals in city and country. 2. A higher percentage of atypical strains of pneumococci have been obtained from healthy persons than from those suffering from pneumonia. In the latter cases the atypical strains may have been overlooked, because of the larger number of typical pneumococci present. Many of the atypical strains seem to be closely related to the streptococci. 3. The so-called Streptococcus mucosus Schottmuller, which has hitherto been classed with the distinct streptococci, is placed as a definite variety among the pneumococci, and it is recommended that the name be changed to Streptococcus lanceolatus, var. mucosus. 4. A lower percentage of strains of pneumococci virulent for rabbits in the doses used has been obtained from normal cases by rabbit inoculations of mass cultures than from cases of pneumonia by the same method. 5. Since the virulence of pneumococci may be rapidly increased for a susceptible species of experimental animal by successive passage, and since pneumococci obtained from most pneumonias are more virulent for experimental animals than are those obtained from healthy individuals, therefore the virulence of pneumococci from cases of human infection is probably increased for human beings; hence cases of pneumonia should be considered to a certain degree as contagious and, since the virulence of the pneumococcus may be quickly increased and since the organism is very prevalent in normal sputum, all possible measures should be taken to restrict public expectoration. 6. By repeated inoculations into sheep of a pneumococcus strain, a specific protective power of this serum for mice is developed against the homologous strain and against certain other strains, one morphological variety (Streptococcus lanceolatus, var.mucosus) being thus clearly differentiated from other strains. 7. Coincident with this production of protective power, a slight specific increase of the sheep serum in phagocytic power in vitro has been observed with some strains of pneumococci, all strains of Streptococcus lanceolatus, var. mucosus, acting similarly with the serum produced by the inoculation of one strain; the strains of some other varieties, however, have shown no definite relationship between the phagocytic power and the protective power of the serum.

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gation such a study was made of normal defibrinated pig's blood under ordinary conditions, on the one hand, and after radiation with rays of various wave length on the other hand.The tests were performed by measuring the growth of liviiig seedlings of the plant Lupinus albus immersed in definite nutrient solution with and without admixture of one per cent of blood. Specimens of pig's blood were exposed to the action of ultraviolet rays for periods varying from 10 to 30 minutes, the radia-

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