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other hand, cases of acute pharyngitis, follicular and non-specific tonsillitis, are among the common diseases of the Colony. I have repeatedly been asked to decide as to the presence or absence of the B. diphtheriæ in such cases-an important result from the point of view of treatment.
5. Experiments with Formalin as a Gaseous Disinfectant.-In the past gaseous disinfect- ion was in great favour and deemed to be the most radical method of dealing with outbreak of epidemic disease. Such an idea was firmly clung to, owing to the prevalence at that time, of the theories of contagion and miasma. Now-a-days with the change in our con- ception of the spread of infectious disease, it becomes obvious that gaseous disinfection is not so reliable as formerly believed. Indeed there is good reason to believe that it is not of much value.
During the past year, Dr. PEARSE, the Medical Officer of Health, carried out several experiments in regard to the efficiency of formalin gas as a reliable germicide. Within recent years this gas has cuine into general favour as a gaseous disinfectant. The micro- organisms used by Dr. PEARSE for his experiments were supplied by me and the different tests arranged for in the following way. Sterile Petri's plates were smeared with different micro-organisms. These were exposed for varying lengths of time to the action of the gas. Thereafter the plates were forwarded to me, and the necessary bacteriological test applied.. In the majority of instances the plates were found to be sterile, thus showing that Formalin' gas, when used in the laboratory, was efficient as a germicide.
In addition to these experiments several other tests were made by myself, in order to show whether we possess, in Formalin, a disinfectant of great value. The results of my enquiry into the question show that, although the general results of experimentation prove Formalin to be an excellent germicide when tested in the laboratory, much doubt exists as to the efficiency of the gas when used for general house disinfection. The condition of affairs. obtainable in the laboratory is by no means comparable to that found in actual practice. The factors which bring about such a failure in the efficiency of gaseous disinfection in general practice, would appear to be the following:-
(1.) In a room to be disinfected, about 60-80 per cent. of the disinfecting gas is
lost.
(2.) An important factor is the difference between the specific gravity of the gas
and the air in the room.
(3.) It is almost impossible to obtain an equal distribution of the gas. (4.) Micro-organisms, in the dry condition can scarcely be killed by a gaseous disinfectant Moisture must be present. Formalin, although the fashion- able gaseous disinfectant of the present day, fails in a good many ways as a disinfectant.
It is one of the best inhibitors of the multiplication of germ life, even in albuminous. solutions. Unfortunately, however, it is but a meagre bactericidal agent. Again, it has an advantage over many gaseous disinfectants in that its specific gravity is approximately that of the air, thus ensuring an intimate admixture of gas and air. However, such valuable property as this is completely counterbalanced by the fact, that. Formalin gas has practically no power of penetration; thus it can be used for surface disinfection only.
With these remarks it is evident that Formalin, although highly commended as the result of laboratory experiments must yield us unsatisfactory results when used for general house disinfection owing to its limited bactericidal powers and its failure to penetrate beyond the surface of any article requiring thorough disinfection.
6. The Strength of Disinfectants.-During the past year, a considerable amount of attention has been given to the question of disinfectants (chemical). Quite a number of these fluids have been examined bacteriologically in order to estimate their carbolic acid co- efficiency, with the hope of arriving at some conclusion as to the most efficient disinfectant which may be used in conjunction with general cleansing.
Up to the present time, great confusion has constantly arisen as to the warranty of the efficacy of a chemical disinfectant. It may be said that there exists no proper official con- trol over the sale of such disinfectants, a condition of affairs likely, at some time, to lead to a false sense of security on the part of the general public, who only too readily fortify them- selves against plague and other infectious diseases, by the liberal use of some disinfectant in their immediate surroundings. Disinfectants, as sold by different manufacturers, have no proper guarantee of their potency. They all vary in their germicidal power, and different samples of the same disinfectant are known to give very varying bacteriological results. During the past three years, an entirely new test for the bacterial determination of the