The first distinctions of the pulse are derived from the extent of the diastole, according to its three dimensions, namely, length, breadth, and depth. These give rise to the characters _long_, _broad_, and _deep_ or _high_. Le Clerc renders the last by _élevé_. A long pulse, of course, refers solely to the impression on the finger, as in reality one pulse cannot properly be said to be longer than another; but when a person is lean a larger portion of the artery can be felt under the finger than when he is fat. The character _deep_ or _high_ is easily understood, and is evidently produced by a free dilatation of the artery. It does not indeed appear evident how there can be a difference between a _deep_ and a _broad_ pulse, if the dilatation of an artery were equal on all sides; but Galen positively affirms that it is a fact ascertained by ample experience, that sometimes there is a free dilatation of the artery upwards with a contracted one laterally, constituting a _high_ and _narrow_ pulse; and, on the other hand, that there is often a free dilatation laterally with a contracted one upwards, constituting a _low_ and _broad_ pulse. He gives directions for detecting these peculiarities of the artery. (De Diff. Puls. iii, 2.) The characters of _quick_ and _slow_ are derived from the length of time occupied in the actions of systole and diastole. They seem to be sufficiently well marked, and yet Fyens denied that there is any difference between _frequency_ and _quickness_. However, many of our late authorities in medicine acknowledge a distinction between these two characters, and they appear to us sufficiently obvious. In fact, Galen establishes the distinction in the most satisfactory manner. (De Dignos. ii.) The distinctions of _strong_ and _feeble_ are derived from the force with which the artery strikes the finger. No one can possibly mistake them. The relaxation and constriction of the arterial tube give rise to the characters of _soft_ and _hard_, which are so obvious that they cannot be misunderstood. The character of _hardness_ is called _tension_ by Galen, who states that it is characteristic of inflammation. The next class of pulses derive their characters from the time which elapses between two diastoles or pulsations of the artery. They are called _dense_ and _rare_, in the ancient system, being used in the same sense that _frequent_ and _slow_ are in modern works. The terms _equal_ and _unequal_ (or, as they might have been translated, _equable_ and _unequable_) arise from the constancy or inconstancy of any peculiar character of the arterial pulsation. The _regular_ and _irregular_ are distinguished from these, inasmuch as a series of pulsations, although unequal may be regular, when they observe a certain ratio, as when four strong pulsations are succeeded by a feeble one, and this series goes on successively.