1. Forty-two cases of congenital morbus cordis are reported with detailed observations on 15 selected cases. 2. The supposed rarity and extreme gravity of the lesion is doubted, it being shown how the clinical signs may be out of all proportion to the anatomical changes present. 3. Etiology: - A familial tendency to congenital heart disease is admitted - rare cases being reported from the literature and one from the writer's experience. It is not thought that there is any significant tendency to parental transmission of acquired organic morbus cordis. Syphilis is undoubtedly a causal factor but not to the extent believed by the French writers. The effect of alcohol is theoretical and the incidence of consanguinity is estimated to be little higher than that of the whole population. The frequent co- existence of visceral and cardiac anomalies and the types of certain congenital cardiac defects suggest that many are developmental in their inception. 4. The physical standard, apart from the cyanotic group and the graver anomalies, is little affected nor is the standard of response to education. Comparisons are made with consecutive series of normal children and sufferers from morbus cordis of rheumatic origin. 5. The theories of the causation of cyanosis are reviewed, its etiology being seen to be dependent on certain "determining factors", namely the degree of shunt present, the efficiency of pulmonary oxygenation and oxygen reduction in the tissue capillaries. 6. The importance óf cardioradiology is stressed. awe A description of the normal cardiac shadow^ the respective merits of teleoradiography, percussion and palpation in determining the size of the heart are given. It is shown that the conception of increase in the heart size is arbitrary, it being affected by the position of the heart in the thorax, the shape of the heart and its relationship to the chest size. The radiographical appearance of the pulmonary artery in its relationship to the oesophagus is described. 7. Defects of the auricular septum are common and in the majority of instances "silent ". Closure of the septum is described as occurring at any date from two weeks to two years after birth, 83.8% closing by the end of the first 10 weeks, and 5.7% being still patent at the end of the first year. The foramen ovale is the common site of patency, defects of the upper and lower parts being rare and complicated by other anomalies in adjacent cardiac structures. With gross defect cyanosis may be present, one case of which is described (Case No.15, vol.2, p.50), and physical and mental development be seriously interfered with. In the major number it is clinically silent and only demonstrable on X -ray examination. 8. Maladie de Roger is, apart from defect of the auricular septum, the commonest of congenital cardiac lesions. The site of election is at the base of the interventricular septum, but may occur elsewhere. In 80% of cases the site of maximal intensity of the bruit lies between the third and fourth intercostal space; it is harsh and high pitched and is conducted transversely and to the back. Thrill is not constant, being absent in two cases in the present series of 9. The radiological picture is characteristic, namely the globular appearance of the heart. The appearance of the conus of the right ventricle and of the pulmonary stem is described, the former is thought to be dilated and in many cases the pulmonary artery also. The diagnostic point is thought to depend on the X -ray picture, and the intensity of the pulmonary second sound; a dilated "pulmon- ary arc" with an accentuation of the pulmonary second sound being indicative of a dilatation of the pulmonary stem, whilst a similar radiological appearance when associated with a normal pulmonary second sound, suggests dilatation of the conus of the right ventricle. Cyanosis is rare, but may occur as either a temporary or a terminal feature. The bruit is to be diagnosed from exocardial and other systolic murmurs of unknown origin, mitral and aortic stenosis and Eisenmenger's Syndrome. 9. "Pulmonary stenosis". The more fitting name of Pulmonary Obstruction is given, it being believed that the clinical signs of pulmonary stenosis and atresia, whether developmental or inflammatory in origin, and the effect on the cardiac septa, are solely determined by the degree and date of obstruction at the pulmonary is valve. The condition classified and described according to this conception. a) Pulmonary obstruction with closed cardiac septa is ;held to be in all instances inflammatory in origin. The pulmonary artery is small or very rarely dilated. The characteristic clinical signs are those of cardiac right side enlargement, a systolic bruit heard over the pulmonary valve and carried up towards the left clavicle and in 50% of cases thrill. b) Fallot's Tetralogy comprises the largest group of defects as associated with obstruction at the pulmonary' valve. Cyanosis is persistent, a count of 13,470,000 being reported; the incidence of thrill varies from 9.1% to 16.5% of cases. The radiological picture is characteristic, namely, a concavity of the upper left cardiac margin an enlarged right heart surmounted by an aorta whose shadow is broad and extends unduly to the right. The freedom of the oesophagus from pressure by the pulmonary artery and its increased liability to pressure from the dilated aorta is shown. The auscultatory features are described and the insignificance of a carotid bruit is stressed. c) A description of the various types of pulmonary imperforation is given. 10. Prognosis is held to depend on :- (1) The local mechanical effects of the lesion. (2) The pathological conditions to which the subject is more liable by reason of the cardiac defect, viz: bacterial endocarditis in about 33.4% of cases, pulmonary tuberculosis, bronchitis, bronchopneumonia and paradoxical embolism. (3) The response of the individual to certain physiological events such as pregnancy and puberty. 11. Treatment of Congenital Morbus Cordis is threefold. a) To prevent intermarriage of and procreation from those persons whose type is believed to favour the incidence of congenital heart disease - alcoholics, syphlitics and congenital syphlitics, blood relations, mental defectives etc; parental acquired heart disease is not thought to play a part. b) To guard the patient against any condition which might raise the pressure of the lesser circulation and to keep him within the limits of his cardiac reserve force. c) To have recourse to the free use of oxygen and warmth in emergency. Recent advances in surgical treatment of congenital valvular defects and the intra-arterial and intravenous use of oxygen are referred to.