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[1912] were induced by its existence to turn their attention to the oxytocic activity, and they devised the method of assay with the isolated uterus of the virgin guinea-pig, and this is now probably the method most extensively employed. Hogben, Schlapp and Macdonald [1924], in elaborating their method of pressor assay on the spinal cat, were able to show that for small doses up to 2 mg. of dried posterior pituitary substance, the period of tolerance did not exceed 1 hour.Little is known concerning the factors responsible for the tolerance, but Dale and Laidlaw [1912] surmized that it might be the consequence of a slow disappearance of the active principles from the blood. On the other hand, it seemed possible that an effect on the blood volume was to some extent concerned. Underhill and Pack [1923], giving "pituitrin" intravenously to dogs, found a 20 p.c. reduction in hEemoglobin occurring both with and without the simultaneous administration of water.In the experiments to be described here, the disappearance of the active principles from the blood has been followed, its relationship to the tolerance investigated and the effect of the principles on the blood volume is examined. The excretion of the pressor principle in the urine is studied quantitatively, and the destructive action of tissue extracts on the oxytocic and pressor activities demonstrated.

In a previous paper (Snow et al., 1955) the pathological findings in the hearts of twenty-five patients with coronary disease were described. In the present paper these findings, together with those in an additional seven patients, are correlated with the clinical features.Material. Thirty-two patients were studied, all with clinical evidence of ischaemic heart disease. Those in whom hypertension or valvular lesions may have contributed to the ischkmic symptoms were not excluded. Sixteen of the patients had been under the care of the Department of Cardiology and all had been observed personally by one of us; 11 had been under the care of other units of Manchester Royal Infirmary, and 5 had been admitted to Crumpsall Hospital, Manchester. Only cases with a full clinical history were included in the series, which was not consecutive.Symptoms occurring within three months of death were the main basis of this study since up to this time the age of a myocardial infarct can be estimated pathologically and correlated chronologically with the clinical events.At necropsy the coronary arteries were injected with a radiopaque medium and radiographed to locate all occlusions; the myocardium was then serially sectioned and all lesions examined histologically by the technique previously described (Snow et al., 1955). RESULTSAge and Sex Distribution. The series included 29 men and 3 women whose ages ranged from forty-one to seventy-eight, with a maximum incidence in the sixth decade. This accords with the age incidence of coronary disease found by other authors (Master et al., 1939; and Friedberg, 1950).The Symptoms of Coronary Occlusion. Of the 53 occlusions only seven occurred without infarction and all these seven occlusions were in arteries supplying previously infarcted areas. In none of these seven were any clinical symptoms associated with the occlusions but, since it is not possible to assess the age of occlusions accurately, these findings should be regarded only as suggesting that occlusion without infarction may be asymptomatic.The Symptoms of Myocardial Infarction. Seventy-seven infarcts were present of which 52 were recent (i.e. less than three months old) and could be accurately correlated with the symptoms. The other 25 infarcts were healed and of indefinite age so that chronological correlation was impossible.Of the 52 recent infarcts, 28 (54%) corresponded with episodes of prolonged cardiac ischemic pain, two (4%) with the onset of angina of effort and two (4%) with the onset or aggravation of dyspncea. Nineteen infarcts (36%) gave rise to no apparent symptoms, and one occurring while the patient was comatose is excluded.Although accurate chronological correlation with the symptoms was impossible in the case of the 25 healed infarcts, it was interesting to note that thirteen could have corresponded with the onset of angina of effort, three with the aggravation of existing angina, six with prolonged cardiac pain, and one with the onset of dyspnea. In two no symptoms were recorded.Asymptomatic and Atypical Infar...