Abstract
Twenty-three patients exhibiting coronary insufficiency on exercise have been studied at rest and at exercise prior to and following sublingual administration of nitroglycerin. The most consistent and marked effect of nitroglycerin was the reduction in pulmonary artery pressure, total pulmonary resistance, and right ventricular work at rest and during exercise. Our patients were grouped according to the degree of left ventricular failure as indicated by the abnormality of rise in pulmonary artery pressure during exercise. It became evident that nitroglycerin improved left ventricular function in terms of increased output and lessened pulmonary artery pressure in cases in which failure was most severe.

ALTHOUGH NITROGLYCERIN has been effectively used for the relief of angina pectoris since its introduction by Brunton in 1867,1 there still remains considerable uncertainty as to its mechanism of action. 2 6 In light of the questionable effects of nitroglycerin on the diseased coronary circulation, attention has been directed toward its other hemodynamic effects.7 8 We wish to report the effects of nitroglycerin on systemic and pulmonary hemodynamics during rest and exercise in patients with coronary insufficiency.
Methods
Twenty-three patients, all of whom exhibited electrocardiographic evidence of myocardial ischemia during exercise, formed the basis of this From At rest, the cardiac index increased 2 and decreased 14% in groups A and B, respectively.
The reduction in cardiac index in group B was statistically significant. On exercise, the cardiac index increased 22 and decreased 4% in At rest, the pulse rate increased 16 and 18% in groups A and B, respectively, which was statistically significant. On exercise, the pulse rate decreased 3 and increased 6% in groups A and B, respectively. These changes were not statistically significant.
Brachial Arterial Pressure
At rest, the mean brachial arterial pressure decreased 8 and 7% in groups A and B, respectively, and was statistically significant in both groups. On exercise, the brachial arterial pressure decreased 14 and 9% in groups A and B, respectively; this was statistically significant.
Pulmonary Arterial Pressure (Fig. 2) At rest, the mean pulmonary arterial pressure decreased 38 and 25% in groups A and B, respectively. On exercise, the mean pulmo- Total Pulmonary Resistance (Fig. 3) At rest, the pulmonary resistance decreased 34 blood volumes in the patient under study. Thus, the patients exhibiting evidence of more severe degrees of left ventricular failure showed no alteration in cardiac index at rest following nitroglycerin but showed actual improvement in cardiac index following exercise after nitroglycerin. Cardiac function was generally abnormal in group B, but less so than in group A, and the resting cardiac index was reduced significantly, but exercise cardiac indices were essentially unchanged before and after administration of nitroglycerin.
Helmholtz on Storage and Retrieval of Data, 1895 I have already noticed the enormous mass of materials accumulated by science. It is obvious that the organization and arrangement of them must be proportionately perfect, if we are not to be hopelessly lost in the maze of erudition.
The learning buried in catalogues, lexicons, and indexes looks as bare and uninviting as the soil of a farm; the uninitiated cannot see or appreciate the labour and capital already invested there; to them the work of the ploughman seems infinitely dull, weary and monotonous. But though the compiler of a lexicon or of a system of natural history must be prepared to encounter labour as weary and as obstinate as the ploughman's, yet it need not be supposed that his work is of a low type, or that it is by any means as dry and mechanical as it looks when we have it before us in black and white. In this, as in any other sort of scientific work, it is necessary to discover every fact by careful observation, then to verify and collate them, and to separate what is important from what is not. All this requires a man with a thorough grasp both of the object of the compilation, and of the matter and methods of the science, and for such a man every detail has its bearing on the whole, and its special interest. 

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