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1. Cultures of Diplococcus pneumoniæ, Bacillus coli, Bacillus fluorescens liquefaciens and Bacillus prodigiosus, when grown in meat infusion broth exhibit an initial latent period when the culture used for inoculation is no longer growing at its maximum rate; if, however, the culture is growing at its most rapid rate the bacteria, upon subculture, show no latent period but continue to multiply at the same rate as that of the parent culture. 2. If broth cultures of pneumococcus are centrifuged at the beginning of the period of maximum rate of growth, the bacteria remaining in the supernatant fluid continue to grow at a rapid rate upon further incubation; if, however, the culture is centrifuged at the end of the period of maximum rate of growth, those bacteria which remain in the supernatant fluid show a prolonged latent period, during which many of the organisms die. While the death of these bacteria is taking place the process follows closely the law of unimolecular reactions. 3. Actively growing pneumococci inoculated into the supernatant fluid from a 4 day culture of the same strain continue to grow rapidly for an appreciable time after inoculation. 4. Filtrates from 24 hour cultures of pneumococcus inhibit the further growth of actively growing pneumococci when the latter are inoculated into such filtrates. This inhibitory action of the filtrates is lost in part as the culture from which the filtrate is obtained is allowed to incubate longer. 5. Actively growing pneumococci, after exposure at low temperatures to the action of the filtrate of a 24 hour broth culture of the same strain, show a greater lag than the controls. 6. The foregoing facts offer strong support for the view that lag is an expression of injury which the bacterial cell has sustained from its previous environment.

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1. Serum taken from recently recovered cases of poliomyelitis may be employed in its treatment and probably yields the best results. 2. When sterile for ordinary bacteria, free of corpuscles and hemoglobin, and when injected by the gravity method, observing well known rules of caution, it may be employed without danger. 3. The serum should be injected both intraspinally and intravenously, the latter either directly or by way of the subcutaneous tissues. 4. The earlier in the course of the disease the serum is employed in suitable doses, the more promise there is of benefit. 5. The action of the serum appears to be more precise and definite in arresting paralysis than in rapidly bringing about its retrogression. 6. The decision to employ the serum should rest upon a clinical examination supported by the results of the microscopic and chemical study of the cerebrospinal fluid. 7. The question of multiple and repeated injections of the serum has not yet been worked out. In the cases here reported and especially in the group in which no paralysis existed at the time of the first injection, the pathologic process either did not progress at all, or where there was extension, as in Cases 14 and 15, the upper segment of the spinal cord became rapidly involved, and was followed by respiratory paralysis and death. Probably in cases in which some degree of muscular weakness develops soon after the injection of serum, reinjection 12 to 24 hours later may be advantageous. The temperature curve may serve to indicate the time for reinjection. 8. The favorable results thus far achieved in human beings by means of the immune serum support and extend those obtained experimentally in monkeys and indicate, as was foreseen, that the milder or less fatal form of poliomyelitis appearing in man is even more amenable to the serum treatment than is the highly fatal disease produced by inoculation in monkeys.

For convenience the results are summarized in tabular form. Table I shows a comparison of the primary reaction in the groups of female and male rabbits inoculated intradermally. In Table II the incidence of metastatic lesions is shown in the various groups of animals. In Table III are shown the character and date of appearance of the generalized lesions (exclusive of orchitis) in the various groups of animals. The results presented in Tables I, II, and III, together with a study of the individual protocols, permit the following general statements to be made relative to the effect of the factors studied upon the course of experimental syphilis in the rabbit. Sex.—In the group of females inoculated intradermally the lesions at the site of inoculation were in general less marked than in the group of males similarly inoculated. Moreover, they attained their maximum size earlier and began to recede earlier than was the case in the males. In none of the females was there clinical evidence of the production of generalized lesions, while in the corresponding group of males metastatic lesions of skin or bones detectible by clinical examination occurred in one instance, or 14.3 per cent. In both groups there was wide variation in the character of the initial reaction in individual rabbits and in the time required for it to reach its maximum size. See PDF for Structure Age.—In the five young males inoculated intratesticularly the disease was not greatly different from that observed in the older males similarly inoculated. The initial reactions were slightly slower in making their appearance, but the magnitude of the reaction, as judged by enlargement of the testicles, was somewhat greater. The percentage incidence of metastatic orchitis was almost the same in the two groups. The younger animals showed a slightly greater incidence of generalized lesions involving structures other than the testicles, although the difference was insignificant, but the lesions were smaller, fewer in number, and confined entirely to the skin, and there was no instance of severe generalized lesions. Moreover, the occurrence of metastatic lesions (skin) in the younger animals was definitely delayed. Method of Injection.—In the animals inoculated by the intratesticular route the development of the primary reaction and the incidence of generalized lesions involving skin and bone were much greater than in See PDF for Structure the animals inoculated intradermally. Thus, of the latter group only one, or 14.3 per cent, showed a secondary metastatic lesion (skin), while in the group inoculated by the testicular route the incidence of metastatic skin and bone lesions was as high as 71.4 per cent. The difference in the character of the disease exhibited by these two groups of animals inoculated in a different manner is quite striking. Intratesticular inoculation produced a much more violent local reaction and a much greater incidence of generalized lesions than did intradermal inoculation. Effect of Castration.—In the group of animals with unilateral orchitis in which the infection was allowed to run its course without any attempt at suppression by removal of the initial focus, metastatic lesions appeared more promptly and in slightly greater incidence than See PDF for Structure in the group of animals in which the initial local reaction was suppressed by removal of the focus itself through castration. The percentage differences are not very great, but they are constantly in favor of the first group, as is the time interval of appearance. This experiment is not in strict accord with similar experiments observed by Brown and Pearce (3) in the past, and while the reasons for this difference are not clear the fact may be noted that the incidence of generalized lesions in uncastrated animals is somewhat higher than that reported by these authors, also that there was a high percentage of recurrence of primary lesions.