Conditions of the Martian atmosphere and surface in the remote past and their relevance to the question of life on Mars

Although the Viking Landers failed to find any evidence of life on the surface of Mars, much remains unknown. Study of returned samples can answer some of these questions. The search for organic compounds, the building blocks of life forms based on carbon chemistry, should continue. The question of life on Mars is still an open one, and deserves to be addressed by the study of returned samples. Whether life developed and evolved on Mars or not depends critically on the history of the Martian atmosphere and hydrosphere. The exobiology of Mars is thus inextrically intertwined with the nature of its paleoatmosphere and the ancient state of the planet's regolith, which may still be preserved in the polar caps and underground. Core samples from such sites could answer some of the questions

An Investigation into the Value of Venography with Special Reference to Varices in the Lower Limb

In Part I,the history of venography was reviewed, the scope of the Writer's investigations indicated, and some general observations on technique discussed. In Part II, a description was given of the findings in 134 venograms performed on normal legs using different techniques, particular attention being paid to absence of filling and incomplete filling of the deep veins. With regard to the former, it was found that while certain techniques demonstrated patency of the deep circulation from the ankle to the groin in every instance, no technique could be relied on to fill all the deep veins; with regard to the latter, four different ways in which this could occur were described, and it was pointed out that the appearances so produced were indistinguishable from those hitherto ascribed to acute deep thrombophlebitis. It was concluded that, while venography is capable of demonstrating patency of the deep circulation of the leg, it must be extremely unreliable in the diagnosis or exclusion of acute deep thrombophlebitis. In Part III, an account was given of the elaboration in venographic technique required to demonstrate the deep circulation of the leg when the superficial veins are varicose and the ankle oedematous, and, with particular reference to the deep circulation, the results of venograms performed on 36 cases of varicose ulceration, and 26 cases of post-phlebitic ulceration, were described. It was found that the deep circulation was patent from the ankle to the groin in every instance, and that in 11 cases of post-phlebitic ulceration the normal deep veins had been replaced by tortuous leashes of incompetent blood vessels. The clinical and venographic findings were correlated, and it was concluded that, since the superficial varices are not compensatory, a history of deep thrombophlebitis in the leg concerned should not be regarded as a contraindication to radical obliteration of varicose veins. In addition, the results were described of retrograde injection of an opaque medium into the femoral vein in 23 normal legs. It was found that,in 16 instances, extensive retrograde flow occurred, and the conclusion was reached that this finding should not be regarded as indicating congenital incompetence of the valves of the deep veins. In Part IV, techniques for the demonstration of the communicating veins in the lower limb were described, and the appearances of competent and incompetent communicating veins illustrated. The results of venographic examinations performed on 40 patients for the identification of communicating veins in the thigh, and on 35 patients for communicating veins below the knee, were compared with the results of clinical tests, and with the operative findings. It was concluded that venography provides a very accurate method,both for identifying the exact position of communicating veins, and for determining whether or not they are incompetent, although the venographic opinion regarding competency is less reliable for communicating veins below the knee than for those in the thigh. In Part V, a description was given of venographic and clinical investigations on 33 patients suffering from recurrence of varicose veins after the operation of high ligation of the internal saphenous vein. The venographic techniques used in demonstrating the different methods of recurrence were discussed, and the clinical and vemographic results were compared with the operative findings. It was concluded that, in this type of case, venography may be of considerable assistance in clarifying the diagnosis, and so influencing subsequent treatment