HALOGENS AND THEIR MODE OF ACTION
The extensive use of various forms of chlorine and iodine as antiseptics has resulted in the accumulation of much information about efficiency of these halogens under various circumstances. There has been considerable study given to the factors affecting their germicidal activities and to the mechanisms of these effects.' Much less is known about bromine?. a* The qualitative similarities and quantitative differences in many of the properties of chlorine, bromine, and iodine afford an excellent opportunity for observing the effects of certain isolated factors on germicidal activity. Accordingly, this paper will be concerned, for the most part, with the extent to which a few basic chemical properties of the halogens, such as hydrolysis, ionization, and formation of complexes can be used to explain quantitative dfierences in antiseptic power. The mechanism of the reactions leading to the death of the organism will not be discussed here. The interested reader is referred to another paper in this series and to a published report6 for information on this subject. One would expect that the rate of bactericidal action would be characteristic of the particular halogen compound present. Under usual conditions of use, however, one may have present, in addition to elemental halogen, hypohalous acid formed by hydrolysis, hypohalite ion from ionization of the acid, complex ions involving elemental halogen with halide ion, and N-halogen compounds. Furthermore, factors such as concentration, pH, and temperature should have quantitatively different effects on the germicidal activities of the three halogens because the equilibrium constants of the reactions involved are different. Most of the work leading to quantitative conclusions has been carried out with bacterial spores, beginning with Levine and co-workers,6 Meyers,' Tilley and Chapin: and others. The advantages of using B. metiens spores, for example, have been pointed out by Charlton and Levine9 and need not be enumerated here. Accordingly, in FIGURE 1, we consider the comparative action on B. meliens spores over a suitable concentration range of chlorine,'O bromine, and iodine" at pH 7 and room temperatures. A solution of each halogen free of added halide was added to a buffered distilled water suspension of spores, extraneous organic matter being excluded as far as possible. The log of the time for 99 per cent kill is plotted against the log of the normality of the solution. Calculation shows that under these conditions chlorine exists chiefly as hypochlorous acid and bromine entirely as hypobromous acid, but iodine is present as molecular iodine. It is then not surprising that the usual order of halogen reactivities is not found and that iodine fails to show less germicidal power than bromine. It might be of some interest to note that on a weight concentration basis, iodine is considerably less active than chlorine, although still more active than bromine. Against
Direct-current bactericidal effect on intact skin
Positive carbon-containing electrodes conveying 5 or more microA of constant direct current per cm2 showed bactericidal activity on intact back skin of 13 human subjects. This effect increased with the duration of stimulation up to a total surface bacterial kill at 20 h. When total current and current density were varied independently on 16 sites on the backs of eight subjects, the effect was dependent on current density, not on total current. Electrodes driven by similar voltages but which removed the electrochemical reaction from inoculated sites on the backs of three subjects failed to reduce the numbers of colony-forming units as compared with those sampled from control sites. This showed the bactericidal effect to be electrochemical in origin, probably mediated by local acidity generated at the surface of the positive carbon-containing electrodes. With an adhesive tape stripping technique on three sites on each of six subjects, it was determined that the effect extended into the epidermis of the human back. No effect was observed beneath negative or control electrodes under the same conditions.
Early Missionaries and the Ethnolinguistic Factor During the ‘Invention of Tribalism’ in Zimbabwe
There is evidence from across the disciplines that at least some of the contemporary regional names of African tribes, dialects and languages are fairly recent inventions in historical terms. This article offers some evidence from Zimbabwe to show that missionary linguistic politics were an important factor in this process. The South African linguist Clement Doke was brought in to resolve conflicts about the orthography of Shona. His Report on the Unification of the Shona Dialects (1931) shows how the language politics of the Christian denominations, which were also the factions within the umbrella organization the Southern Rhodesia Missionary Conference, contributed quite significantly to the creation and promotion of Zezuru, Karanga and Manyika as the main groupings of dialects in the central area which Doke later accommodated in a unified orthography of a unified language that was given the name Shona. While vocabulary from Ndau was to be incorporated, words from the Korekore group in the north were to be discouraged, and Kalanga in the West was allowed to be subsumed under Ndebele. Writing about sixty years later, Ranger focusses more closely on the Manyika and takes his discussion to the 1940s, but he also mentions that the Rhodesian Front government of the 1960s and 1970s deliberately incited tribalism between the Shona and the Ndebele, while at the same time magnifying the differences between the regional divisions of the Shona, which were, in turn, played against one another as constituent clans. It would appear then that, for the indigenous Africans, the price of Christianity, Western education and a new perception of language unity was the creation of regional ethnic identities that were at least potentially antagonistic and open to political manipulation. Through many decades of rather unnecessary intellectual justification, and as a result of the collective colonial experience through the churches, the schools and the workplaces, these imposed identities, and the myths and sentiments that are associated with them, have become fixed in the collective mind of Africa, and the modern nation states of the continent now seem to be stuck with them. Missionaries played a very significant role in creating this scenario because they were mainly responsible for fixing the ethnolinguistic maps of the African colonies during the early phase of European occupation. To a significant degree, these maps have remained intact and have continued to influence African research scholarship.