292 BRITISH PHYSICIANS. of a poison introduced into the system, he is of opinion that the only security lies in the preven™ tion of the disease, by the excision of the bitten part at any period before constitutional symp- toms have commenced. In this work, as in his Syncope Anginosa, the chief object was to esta- blish pathognomic distinctions, by which the nature and symptoms of the disease might be accurately determined, as the safest guides for the adoption of remedial measures, more perfect and effectual. In 1816, Dr. Parry published his last medical work, " An Experimental Inquiry into the Nature, Causes, and Varieties of the Arterial Pulse, and into certain other properties of the large Arteries in Animals with warm blood." This work, im- portant in its application to physiology, pathology, and surgery, leads to conclusions as to the usual state and relative proportions of the moving powers of arteries very different from those of preceding physiologists. While the experiments fully prove a power of dilatation and contraction not only to exist, but to be owing to a cause partly mechanical, elasticity — and partly vital, or what the author calls tonicity^ he shows that the power which in muscles is called irritability, is entirely wanting in the arterial tubes, which suffer no degree of con- traction from the application of a great variety of chemical and mechanical agents, called stimuli. They further show, that, in the larger arteries, there is no sensible dilatation or contraction from the systole and diastole of the left ventricle of the heart, and therefore that the pulse cannot depend on that alternation ; that the chief cause of the
