In 1836 Dr. Williams was asked to give lectures on Diseases of the Chest at the Anatomical School in Kinnerton Street, connected with St. George’s Hospital. In 1836-7 he was president of the Harveian and the Westminster Medical Societies. In the summer of 1837 he worked to prepare for the second Report of the British Association Committee on the sounds of the Heart, in which were brought forward important experimental results in regard to morbid murmurs associated therewith. In 1835 he had shown that the true ground of distinction between different forms of disease of the heart’s valves lay in the different direction in which the sonorous currents spread the sounds, and imparted them to the chest walls. Thus he first established the distinction between basic and apex murmurs, developing his views more fully in 1836-7-8. In 1839 Dr. Williams was elected Professor of Medicine to University College, and physician to its hospital on Elliotson’s retirement. Work now crowded upon him; in the first winter session he gave 150 lectures and examinations in six months, visited the hospital almost every day, and gave a weekly clinical lecture. Up to this period _post mortem_ examinations at the hospital had been made in a mere open shed, with a wooden shelf, scarcely screened, and without a table or a supply of water. Dr. Williams himself planned a proper _post mortem_ theatre; and with the plan he offered £50 towards the cost,—a munificent mode of action which speedily secured the building of the required theatre. Dr. Williams’s practical teaching and luminous lectures caused the Medical School to increase still more rapidly. He had a class of over two hundred. In 1840 an experimental research in which Dr. Williams was assisted by Prof. Sharpey proved the muscular contractility of the bronchial tubes, and confirmed the great influence of belladonna and stramonium as remedies in asthma, in suspending this contractility. The winter of 1840-1 was occupied largely with original experiments on congestion, determination of blood, and inflammation, which Dr. Williams treated of in the Gulstonian Lectures at the College of Physicians in 1841. His results and views were, as acknowledged by eminent men recently, twenty-five years in advance of his time. Both Virchow and Burdon-Sanderson have acknowledged their great value. Dr. Williams claims that he first pointed to enlargement of the arteries leading to a part as the direct physical cause of determination of blood to that part. “When the web of a frog’s foot is gently irritated by an aromatic water, the arteries may be seen through the microscope to become enlarged, and to supply a fuller and more impulsive flow of blood to the capillaries and veins, which then all become enlarged too: the whole vascular plexus, including vessels which before scarcely admitted red corpuscles, then becomes the seat of a largely increased current” (_London Medical Gazette_, July 1841).