Donald E. H. Frear

Dieldrin: Extraction of Accumulations by Root Uptake

Certain forage crops can absorb and translocate the chlorinated hydrocarbon insecticide dieldrin from soil or sand. An extraction technique routinely used for analyses of residues does not quantitatively remove this internal chemical, but a method employing chloroform-methanol extraction leads to essentially quantitative recovery.

A CATALOGUE OF INSECTICIDES AND FUNGICIDES

The function to which I refer is the amazing ability of the heart to handle large, variable streams through markedly angular passages, at vastly different pressures and rates varying from zero to high speed, without provoking therein measurable eddies. Quite an elementary knowledge of engineering teaches us that the onset of eddies in either inlet or outlet ducts is associated with a material drop in efficiency. As the velocities increase, the production of eddies may be so great that finally they themselves may put a top level at which the system may function. Moreover, there are two different ways in which this may occur. On a low pressure induction system, the top rate of the entry stream may be easily and finally limited, while on the high pressure outflow side, the effects may also be similar where limited power is available or, alternatively, markedly increase the energy consumption per unit of flow. In the living heart, eddies on the very low pressure flow side could very easily cause obstruction leading to acute or chronic venous congestion. On the outflow sides, the development of such eddies would be most importantly connected with a limitation of the total output, both immediately and secondarily, by the onset of unusual cardiac fatigue. There seems little doubt that this function is associated with at least three factors, namely, the curious arrangements of the muscular bundles; the pattern of the nervous discharge; and the properties of the blood itself. It is also conceivable that the odd lining of the ventricles may have a damping effect on eddy formation. Moreover, it seems highly probable that this function is not entirely located in the heart itself, but is also carried out in the main vessels, especially the arteries where eddies would very greatly increase internal friction. As eddies are readily discernible by stethoscope or other devices, their onset has many clinical notations. Those that are not occasioned by gross physical damage and tend to be variable in character are called haemic or organic murmurs. That changes in the blood may cause such eddies is known, especially by certain anemias, but it has not been generally recognized that their normal absence is due to a remarkable cardiac function which may itself become disturbed. Consequently, its full significance both in diagnosis and prognosis has been overlooked. Especially might attention be directed to the fact that increase in the loudness of murmurs by reason of increased work is a clear sign that the efficiency of the heart is materially decreased for such higher loading. Eddy formation in the large vessels would not be heard easily, as they are too deeply situated, but, by effectively decreasing the available flow space, they will load the heart with useless counter-friction work. The markedly decreased ability to compensate for loading by some arterio-scleroties, in the absence of other obvious causes, may be such an example. The importance of eddies in flow systems is very well appreciated in engineering, including electrical, and it seems worth while to recall this neglected factor to students of the circulation, since it has yet to be incorporated in the standard works. 0. S. GIBBS MEMPHIS, TENN.

Extraction of chlorinated hydrocarbon pesticides from plant materials

This review will discuss the methods which have been and are currently being used to extract chlorinated hydrocarbon insecticides from crops. Further, it will point out the possible limitations of these methods particularly when they are applied to crops containing internal residues.