126 



NA TURE 



[Dec. 1 8, 1873 



Galabin persists in not employing, because he thinks^ 

 though the evidence he brings forward on the subject 

 is extremely small — that it increases the number of minor 

 vibratory undulations. Nothing of the kind, however, is 

 the case. Nearly all properly-taken tracings from the 

 pulse in health present, if there is a secondary spring 

 employed, no percussion wave at all ; and when it is 

 present the true predicrotic wave is quite independent, as 

 may be seen in Fig. 2, which is from a powerful, healthy 

 pulse of 44 a minute, in which the rise a is the percussion, 

 b the primary, c the predicrotic, and (/ the dicrotic wave. 

 This true predicrotic wave (varies in development with 



Fig. r. — Sphygmograph tr.icings of healthy puUes, drawn to one scale, with 

 rates between 44 and 170 a minute. They read from left to right. 



different pulse rates, being much more conspicuous in very 

 slow pulses, and entirely absent in very quick ones, in 

 which last a slight percussion wave is frequently found 

 (see Fig. i). l3r. Sanderson has previously described 

 these two waves as co-existing, and he is undoubtedly 

 right, as any who have had any considerable experience 

 in Sphygmography in health will agree. It is Dr. GalabLn 

 who is in error, and it is but little compliment to other 

 workers in the same field even to suppose that they have 

 been sufficiently simple-minded to study and describe as 

 physiological phenomena, instrumental errors so uncom- 

 plicated in origin and so readily comprehended. The 



Fig. 2. — A tracing of a healthy pulse beating 44 a minute. 



chief argument he brings forward in favour of his expla- 

 nation is that by placing a weight on the lever at different 

 parts, and so altering its moment of inertia, the length of 

 the predicrotic wave is varied. That the percussion wave 

 which is developed when no secondary spring is employed 

 is so affected, no one will doubt, because the resistance of 

 the pen is less significant when the lever is heavy than 

 when it is light, and therefore the wave is of shorter dura- 

 tion when it is weighted. This wave, however, is even 

 then of such considerable length that it has not ceased be- 

 fore the true predicrotic wave has commenced, and it 

 therefore disguises the true nature of the trace. It is, 

 therefore, only when the secondary spring is employed 



that a proper trace can be obtained ; because then only is 

 it possible to see the full e.xtent of the true predicrotic 

 wave, uncomplicated by the superposition of the extraneous 

 percussion wave. The latter does not appear as an extra 

 element of the curve, but entirely disguises its true nature, 

 on account of its being developed quite independently, 

 when the lever is no longer in connection with the rest of 

 the instrument, and therefore unaffected by whatever 

 change may be occurring in the artery. 



The cause of this predicrotic wave, which Marey gives 

 of the similar one that appears in the hannadromometer 

 trace (Fig. 3, fi) though considered by Dr. Galabin 

 scarcely worthy of refutation, is supported by a large 

 number of facts, especially by the hremadromometer trace 

 itself (Fig. 3, (I, li). Its commencing in the radia) artery as 

 well as the carotid, at the moment of closure of the aortic 

 valve, is also strongly in favour of the supposition that 

 it is of shock origin ; and that a shock may be 

 transmitted through a column of fluid, which Dr, 

 Galabin and some others seem to doubt, can be easily 

 proved by suddenly closing an ordinary tap through 

 which a large volume of water is passing, whereupon 

 several oscillations of the retained liquid occur, producing 

 a series of blows against the tap and perhaps the side of 

 the tube, which are heard without difficulty. 



The hasmadromometer trace (Fig. 3) shows also 

 how completely the dicrotic wave is the result of the 

 closure of the aortic valve, as Dr. Galabin also thought 



'iG. 3. — Haemadromograph trace rom the carotid, a, Curve of direction 

 and force of blood current, all above the dotted line indicating an onward 

 and all below a heartward stream. f3. Simultaneous sphygmograph 



in his earlier paper ; but in his second he attributes it to 

 the oscillatory result of the inertia of the arterial walls, 

 and the lateral momentum acquired by the blood. The 

 mass of the arterial walls, and the lateral move- 

 ment of the blood during distension are so slight, that 

 neither are in any way competent to e.xplain a move- 

 ment so constant and so considerable as the dicrotic 

 wave, especially when one so much more reasonable is to 

 be obtained as the result of the valve closure. At all 

 events no theory can be considered at all satisfactory 

 which does not explain, in oneway or another, the ha:ma- 

 dromometer trace, which is one of the foundations of 

 arterial dynamics, and has been verified in all its details 

 by Dr. Lortct of Lyons. Neither Dr. Galabin's theory, 

 nor that of Mr. Mahomed, can be said in any way to take 

 cognizance of the facts which it discloses, and they are in- 

 capable of doing so, therefore they must be considered 

 inaccurate. Both these authors complicate their results 

 by arguing from the analogy of a schema or model of the 

 circulation constructed with elastic tubes ; the arteries, 

 however, are not simple elastic tubes, but tubes cut in 

 elastic solids, being surrounded on all sides by yielding 

 tissues, and they are not therefore comparable with tubes 

 experimented on in air, and will not allow of comparative 

 deductions being drawn from them.* A. H. G. 



• The blocks for Figs. I and III .ire kindly lent by Prof. Hump'iry. 



