SUMMARYGenetic transformation was investigated among Neisseria spp. whose normal habitat is the nasopharynx of humans. Seven species, as characterized in Bergey's Manual (1957), were represented. Deoxyribonucleate (DNA) preparations from streptomycin-resistant mutants of N . meningitidis, N . perflava, N . Java, N . subJava, N . sicca, and N . flavescens conferred resistance upon streptomycinsusceptible parent strains of the corresponding species (intraspecific transformation) and of each other species (interspecific transformation). Ratios of interspecific to intraspecific transformation were 0.01 or higher for all possible combinations of DNA and recipient cells of the six species. On the other hand, N . catarrhalis cells, which exhibited high frequencies of intraspecific transformation, were not transformed a t detectable frequencies by DNA from any of the six Neisseria species listed above. In turn, DNA from N . catarrhalis had little or no transforming activity for these other neisseriae.Possible evidence of structural differences between these DNA's was sought by analysing the base contents of transforming preparations. The bases adenine, thymine, guanine and cytosine were present in about equal proportions in the DNA's of the six Neisseria: meningitidis, perflava, Jlava, subJava, sicca and flavescens. In DNA preparations from two strains of N . catarrhalis, however, adenine and thymine predominated. The ratio (adenine + thymine/guanine + cytosine) was higher than 1.4 compared to 1.0 for the others.

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SUMMARYThe base contents of deoxyribonucleate (DNA) preparations from 7 strains of Neisseria catarrhalis were determined chromatographically.Three non-overlapping classes were distinguished by mole yo guanine + cytosine. These centred about the values 41 yo (2 strains), 42.3 yo (4 strains, including ATCC 8193), and 44.5 yo (strain NCTC 4103). Each of the 7 strains was capable of undergoing genetic transformation. DNA preparations from spontaneous streptomycin-resistant mutants of all 7 strains elicited transformation of recipient strains in all 49 possible combinations. Results with this group, therefore, do not support the hypothesis that success in transferring genetic information between 2 strains requires identity of average DNA base contents.Differences of reciprocal transformation frequencies and of 4 physiological characteristics (nitrate reduction, pigment production on vancomycin-containing agar, hydrolysis of gelatin, and growth at 28O) appeared to separate 6 of the strains of Neisseria catarrhah from the seventh (NCTC 4103), which may properly be named N . cinereas.

SUMMARY : Highly polymerized bacterial deoxyribonucleic acids (DNAs) obtained from extracellular and from intracellular locations were analysed. DNAs from two strains (Staphylococcus aureus and S. epidermidis) were of the type having high adenine and thymine contents ; two others (Alcaligenes faecalis and Pseudomonas fluorescens) had a high content of guanine and cytosine. For each micro-organism the composition of extracellular DNA was essentially the same as that of the intracellular DNA. Conditions associated with the extracellular accumulation of DNA in cultures of 3 strains were investigated. S. aureus elaborated a deoxyribonuclease (DNase) which required calcium ion and high pH for activity. In a culture medium of c. pH 6 and insufficient calcium, the DNase was inactive and DNA slime accumulated. In cultures of P . jluorescens a specific ribonuclease-sensitive DNase inhibitor protected slime DNA from depolymerization by culture DNase. In cultures of A . faecalis, also, both a DNA slime and a low concentration of DNase may occur. This enzyme, detected by studying its action against solutions of calf thymus DNA prepared from dried fibres, was activated by various cations within the pH range of cultures. Unlike other DNases, however, it has little capacity to attack the slimelayer DNA, which presumably is more nearly native.

Textbook accounts of this subject are inadequate. This review considers the work of Cooper and Salmon and reproduces some of their figures. Applications in the diagnosis and treatment of cancer are discussed. The largest mammary arteries are the lateral (from the axillary) and the anterior medial and posterior medial (from the internal thoracis). The branches of these arteries do not follow the duct system, but instead form a plexus in the anterior fat layer. Normally there are no hypervascular or hypovascular areas. The contribution of the mammary branches of the posterior (aortic) intercostal arteries is minor. There are superficial and deep sets of veins, the latter associated with arteries. Mammary vessels of living women are demonstrated by infrared photography, thermography, and mammography. In the diagnostic use of these methods there is a tendency to rely upon the concept of normal vascular symmetry, but this is a fallacy.