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.
An inequality may take place in respect to one pulsation; for the dilatation of the artery may be interrupted, and then completed, when it is called dorcadissans, caprizans or goat-leap; or the stroke may be suddenly repeated, when it is called dicrotos, which may be translated the double, reverberating, or rebounding pulse. The term dorcadissans is derived from dorcas, an animal generally supposed to have been the goat, but it is now satisfactorily ascertained that it was the antelope dorcas or gazelle; and, in the Latin translations of Avicenna and Haly Abbas, it is rendered gazellans. It is said that when this animal leaps upwards it at first takes a short spring, then seems to make a sudden stop, and afterwards takes a much larger and swifter bound. This character was applied to the pulse when an imperfect dilatation of the artery is succeeded by a fuller and a stronger one. (Galen, de diff. Puls. i, 28.) It is thus described by Haly Abbas: “Gazellans pulsus est qui cum a celeritate incipiat antequam percussiat stat, dehinc velociter movetur: vocatur autem hujusmodi gazelenus suâ ex similitudine caprioli saltu: quum capriolus quem Gazel Arabicè vocant cum saltum dederit pedes tollit et suspensus pauco videtur tempore atque sic ad terram velociùs redit.” The translator of Alsaharavius renders it by fusalis. It is correctly stated by Fouquet that the second pulsation is necessarily larger than the first. The dicrotos consists of two pulsations, following upon one another so rapidly as to form, as it were, but one beat of the artery. In the translation of Alsaharavius it is called mallearis, and is thus defined: “Est autem pulsus mallearis qui percutit manum et recedit, deinde redit et percutit secundario.”
When there is a succession of pulsations which diminish in magnitude regularly, such a system of pulses is called myuri, that is to say, decurtate or sharp-tailed, from their supposed resemblance to the tapering tail of a mouse. Those who are acquainted with the Scholiast on Hephæstion, and the other ancient writers on prosody, will readily recognize a term with which they are familiar. Galen inclines to the opinion that this state of the artery is connected with an intemperament of the portion where the expansion is limited. Of these pulses, some end in complete asphyxia, and hence are called swooning, failing, or fainting myuri, (Le Clerc renders it by le myurus defaillant;) and others again gradually recover their former magnitude, and are called recurrent myuri. Nearly allied to these are the innuentes et circumnuentes, for which it is scarcely possible to find any appropriate term in English. Le Clerc thus renders and explains this pulse, in French: “Le myurus qui va en baissant de côté et d’autre, c’est a dire qui frappe moins sensiblement le premier et le dernier doigt que celui ou ceux du milieu.” It consists, as Avicenna explains, of a double myurus, which swells out in the middle, and diminishes at both extremities. It was therefore a sort of double inclined plane. The myurus, and the innuens et circumnuens, are thus described by Haly Abbas: “Est autem et in hac specie unius pulsationis pulsus qui muris cauda appellatur; quique inclinus vocatur pulsus. Et qui muris cauda vocatur fit cum arteria dilatatur sub primo digito qui a superioribus est grossa, et sub secundo minus grossa, sub tertio parva, sub quarto minima. Inclinus autem pulsus est qui sub duobus mediis movetur digitis grossus et sub extremis hinc et inde subtilis et tenuis; aut medium ejus elatum est, et extremitates demissæ, videturque tangenti arteriæ extrema ad inferiora declinari.” Sprengel appears to think that the pulsus inclinus of Haly Abbas is one first described by him, but there can be no doubt of its being identical with the innuens et circumnuens (νενυκὼς καὶ περινενευκὼς) of Galen’s system. It is likewise the same as the pulsus inclinatus of Rhases, who says it occurs in hectic fevers and consumption. Galen attempts to explain this pulse by referring it to weakness of the vessel and an unequal wasting of the parts around, which convey the impression, when several fingers are applied together, as if the vessel swelled out in the middle. (De Diff. Puls. ii.)
In the spasmodic pulse, the artery is said to convey the sensation of a string or cord tightly stretched, which, when touched, starts from its place. It seems to be the pulsus tortuosus of Alsaharavius, and is commonly met with when convulsions are impending.
The vibratory derives its name from an imaginary resemblance to the motions of a rod or dart when thrown into the air, and it can only take place when the artery is hard, and the strength good. Le Clerc renders it le pouls dardant. It is generally named thrilling in modern works. According to Actuarius, it is hard, quick, and dense, and indicates inflammation of nervous parts.
The undulatory derives its name from a supposed resemblance to the rolling of the waves, and can only take place when the artery is particularly soft, being accompanied with an unequal elevation of it in the diastole. It is thus described by Rhases: “Undosus vero est qui secundum latitudinem, magnum digiti occupat locum, cum lenitate et repletione, cum eo tamen non est magna elevatio neque subita, sed videtur quod elevationem ejus una post aliam contingit, donec fit ut undis assimilatur, quarum una aliam sequitur.” It is the pulsus fluctuosus of Haly Abbas, and the pulsus fluens of C. Aurelianus. (Morb. Acut. ii, 32.) Le Clerc renders it ondoyant.
The vermicular differs from the last mentioned only in magnitude and strength, being soft, small, and weak. Nearly allied to it is the formicans or ant-like pulse, which is one of the last degree of weakness, smallness, and density. They are thus described by Rhases: “Vermicolosi forma est ut forma undosi, in elevatione quæ secundum diastolem eadem invenitur, non tamen est latus, neque plenus, cujus inundatio existit debilis, qui vermibus per foramen arteriæ discurrentibus assimulatur: formicans vero pulsus adeo invenitur in ultimo parvitatis, et spissitudinis consistere, ut pulsui pueri recens nati assimuletur.” According to Galen the formicans is a pulse which it requires great experience to detect. (De Dignos. Puls. ii, 1.) Haly Abbas states that it is the termination of the vermicular. It is the pulsus formicabilis of Cælius Aurelianus. The Chinese compare the formicans to a silk thread, a capillary tube, or a hair.