Charles James Martin

The Principles involved in the Standardisation of Disinfectants and the Influence of Organic Matter upon Germicidal value

In any method of standardisation it is necessary that the test shall be carried out at a constant temperature, as the disinfection process has a high temperature coefficient. For any method to be of general application, it is also necessary that the temperature selected shall be adhered to in all determinations, since the temperature coefficient of disinfection varies for different disinfectants. The temperature adopted was 20° C. In the case of vegetative organisms a disinfectant varies in efficiency as much as ten times according to the organism against which it is tested. Some disinfectants are more efficient against one vegetative species of bacteria, others against another. The presence of 10% blood serum reduces the efficiency of 1% phenol about 12%. The effect upon emulsified disinfectants is somewhat greater. With mercuric chloride the reduction was much greater, a 0·5% solution being reduced to from 0·6 to 0·06 of its original value as the concentration of serum was increased from 5 to 30%.

The influence of air movement and atmospheric conditions on the heat loss from a cylindrical moist body

It is emphasized that as heat exchange is controlled by the temperature of that boundary layer of molecular dimensions which separates a cooling body from its environment and from which evaporation occurs, attempts to relate heat loss with internal temperature have resulted only in empirical formulae. A rational formula involving the temperature of the evaporating surface is suggested, and it is shown how in the case of a system of sufficient simplicity all the terms can be either measured or derived from experiments. The results of experiments with a small moistened cylinder are detailed illustrating the effect of wind velocity upon evaporative and convective heat loss under the one condition when the evaporating surface remains at constant temperature notwithstanding variations in wind, namely, when the whole system has been cooled to wet-bulb temperature. Evaporative loss is found to vary as V 0.65 , convective as V 0.70 . Experiments are next described showing the effect of wind upon evaporative and convective losses when, the internal temperature being constant, the temperature of the evaporating surface fluctuates in consequence of varying wind velocity. Heat loss now varies very closely as V 0.5 at velocities greater than 1 m./sec. At velocities below 1 m./sec. the same relation of heat loss to velocity obtains if due allowance be made for natural convection. This square root function is fortuitous, and heat loss varied between the square root and cube root of the velocity as the internal conductivity was diminished. Attention is drawn to the impossibility of forming general conclusions from observations on any particular system, as the way in which the rate of heat loss varies with the velocity of the wind depends not only upon the internal conductivity of the system but also on its size and shape. Observations are described showing the influence of varying the internal temperature on total and evaporative heat loss with constant wind velocity and constant atmospheric conditions. These experiments furnish data from which the surface temperature can be derived from measurements of evaporation, and show that the temperature of the surface and the rate of loss of heat by convection are both linear functions of the internal temperature at any one wind velocity. They also show that the values of the constants of the system derived from experiments at the temperature of the wet bulb are applicable when the cylinder is heated. An analysis of the results of the experiments with varying internal temperature indicates that the temperature of the evaporating surface (t s ) is related to the internal temperature (t 1 ) and that of the wet bulb (t w ) by the expression The value of C with varying wind velocity is ascertained by experiments, thus affording another means of arriving at the temperature of the evaporating layer. Values of t s obtained in this way are compared with those determined by observing the rate of evaporation and show reasonable agreement. It is shown how, knowing the temperature of the evaporating layer, the constants of the system employed and the effect of velocity of wind upon heat exchange, the rate of loss of heat by evaporation and by convection under given conditions can be predicted. Instances of the agreement between predicted and observed values are given. From the formula representing the influence of atmospheric conditions on heat loss it can be shown, by calculation, that if the wet-bulb temperature remains constant considerable variations in the temperature of the dry-bulb influence but slightly the heat loss from the moist cylinder. It will be seen that the analysis of the effects of environmental changes on the heat loss from a simple physical system such as was used presents no serious difficulties. Such an analysis, unfortunately, does not enable deductions to be made with reference to systems of different physical characteristics. How observations on such systems can be related in other than a qualitative manner to the effects of corresponding changes on living creature differing in size and shape and degree of moistening of their surfaces is not clear. When account is taken of the ability of living beings to alter the vascularity of their surface tissues and so to vary the temperature of the body surface while other factors remain constant, the difficulties in relating the cooling of any physical system to the loss of heat from animals become painfully apparent. The most hopeful method of assessing the effect of air movement and atmospheric conditions on the heat loss from the human body seems to be in terms of a subjectively determined standard such as the effective temperature scale of Houghton & Yaglou. The validity of such a scale has received support from observations by Houghton et al. (1924) and Vernon & Warner (1932) on the relation of pulse rate, body temperature, metabolism and other physiological variables to “effective temperature”.

Die Dichte und das Lösungsvolumen einiger Proteine

ZusammenfassungEs wurden bei vier Proteinen, nämlich Kasein, Ei- und Serum-Albumin und Serum-Globulin, die direkt an trockenen Mustern bestimmten Dichten und die aus den spezifischen Gewichten konzentrierter Lösungen berechneten Dichten miteinander verglichen. Die letzteren wurden 5–8 Proz. größer gefunden als die ersteren, und es ergibt sich hieraus die Volumskontraktion, welche beim Uebergange dieser Proteine in kolloide Lösung stattfindet.

Memorial to Sir Walter Fletcher.

SIR,-The public life of this country suffered a loss of more than common magnitude through the death of Sir Walter Morley Fletcher, K.B.E., M.D., F.R.S., first Secretary of the Medical Research Council, on June 7th, 1933. He was then in his sixtieth year and in the height of those powers which he had used without stint in the service of science and of mankind. The ideal that he held before him, in words which were frequently upon his lips, was the advancement of knowledge for the relief of human suffering. He strove ever towards this, both in his years at Cambridge as a brilliant investigator and an influential teacher of youth, and later in the administration of the public support provided for medical research and in measures for bringing the results of scientific work more effectively to the assistance of the State. Walter Fletcher gave richly to the common weal, and it is proper that some worthy tribute of an enduring kind should be paid to his memory. The desire to take part in this will be widespread among those who were able truly to appreciate his great labours in the cause of medical science, and will be felt not least by the many research workers who were directly indebted to him for help and inspiration: it will extend, also, to others in different spheres of life who were privileged to enjoy that friendship for which he had so great a gift, and throughout a wider circle of those who admired his vigorous personality and his mastery of practical affairs. It is considered that the tribute should consist in the first place of a personal memorial, and, secondly, of the inception of some scheme for the furtherance of the cause which Sir Walter Fletcher had so much at heart. It is therefore proposed-first to commission a portrait bust, to be placed in a suitable setting in the entrance hall of the National Institute for Mledical Research at Hampstead. The remainder of the sum collected will then be used as a fund for building-at the farm premises of the National Institute at Mill Hill-a Walter Fletcher Laboratory, to be devoted particularly to those nutritional studies in which he was so keenly interested. This will not only provide an appropriate memorial, but it will make an urgently needed contribution to the national equipment for work in what is at present among the most important of all branches of medical research. In view of the wide utility and public value of the second part of the memorial, it has not been thought desirable to suggest for individual subscriptions any limit such as might have been fitting for a tribute of a purely personal character. It is strongly hoped, however, that this will in no way deter those who may wish to have a share in the personal memorial but are of necessity restricted to giving quite small sums. All subscriptions should be sent to the Secretary, Fletcher Memoria! Fund, 38, Old Queen Street, Westminster, S.W. 1.We are, etc.,