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left ventricle, acknowledging, however, previous work by Harvey, Lower, Borelli, Pitcaime, Keill and others. As became every physiologist of his time, he wrote on the "animal spirits" and on the "sympathy" between the nerves; he studied experimentally the physics of respira- tion; he produced pneumo-thorax in the dog, and speculated on the sources of animal heat, agreeing with Boerhaave and the iatro-physical school in attributing it to friction of the blood and blood-cells against the walls of the vessels. He tried to explain the florid nature of arterial blood, but on this point he was not so enlightened as his prede- cessor Lower about sixly years before. He used the microscope in an interesting way to try to gain information as to the cause of muscular contraction in the living frog. He incidentally saw the red blood cor- puscles in the living capillaries and noticed that the diameter of the smallest vessel was equal to that of the blood-disc. He gives the receipt of an injection-fluid for blood-vessels. He continued Harve/s work, by studying the rupturing pressures in blood-vessels and the rupturing strain of various animal flbers. He speculated on the physiology of renal secretion.
In what would now be regarded as pure medicine and even surgery, Hales was just as active. He wrote critically on the therapeutic value of "tar-water"; he wrote on fevers and on the possible effects of fever heat on the blood, actually suggesting that the shivering fit of ague might be due to the too thick blood not passing with ease through the capillaries. He studied the effect of alcohol on the living organism by injecting brandy into the blood-vessels of the dog. He wrote on para- centesis abdominis. Hales spent a great deal of time in attempts to discover satisfactory solvents for stone in the bladder and the kidneys, and actually devised a method of extracting stone from the bladder.
In the physical sciences he wrote on earthquakes, and he invented an instrument for determining the depths of the ocean : this appears to have been of some practical service, but, according to one account, was lost in the West Indies. Hales invented a method for the dredging of harbors. He gives directions for "salting" meat for long voyages.
Hales, as we have seen, was patronized by Frederick, Prince of Wales, the eldest son of George II., who died before his father in 1761. His widow Augusta, daughter of Frederick, Duke of Saxe-Gotha, for the last ten years of Hales^s life the Princess Dowager of Wales, had a great regard for the Reverend Doctor, and there is no doubt that had he so desired it, he might have become a bishop. The utmost he would allow, refusing a canonery of Windsor, was to be made " Clerk of the Closet" or almoner "to the Princess Dowager." After his death, the Princess erected a mural monument in marble to his memory in West- minster Abbey. He is not buried there amongst England^s other great ones, but under the tower of his old church at Teddington. The me- morial is wrought in alto relievo; it represents the figures of Religion