February i6, 1905] 



NA TURE 



375 



1.56 to 2.07. The comet was re-observed on its return in 

 1S7; and in 1879, but has not been seen since. 



U'olf's 18S4 comet is also due at perihelion in April, but 

 the conditions for its observation will be verv unfavourable. 



.Another comet which may return towards the end of this 

 year is the faint one discovered by Prof. Barnard in 1892. 

 It was not seen, however, in 1899, and, as its exact period is 

 doubtful, although probably about b\ years, it may again 

 escape detection. 



Castor a Quadruple Sr.4R. — In a communication to the 

 Astronomical Society of the Pacific [Piihlicalion No. 99) 

 Prof. Campbell discusses the multiple character of Castor, 

 and states that Dr. Curtis, using the Mills spectrograph 

 attached to the 3b-inch refractor of the Lick Observatory, 

 recently discovered that the brighter component of the sys- 

 tem is attended 'bv a faint companion. The fainter com- 

 ponent was shown by M. Belopolsky, in 1896, to be similarly 

 double, so that in Castor we have a quadruple system in 

 which each component of a visual double is attended by a 

 faint companion. The period of the fainter system is about 

 three days, but further observations of the brighter double 

 will have to be made before its period ran be determined. — 

 {Popular Astronomy, No. 2, vol. xiii.) 



BLOOD PRESSURES IN MAN.-" 

 'T'HE lecturer began by contrasting Galen's conception of 

 the oscillation of the blood, about the liver as a centre, 

 with the cardiac circulation of Harvey. The pulmonary 

 circulation — for the purposes of this lecture — was omitted, 

 and attention directed exclusively to that in the systemic 

 arteries. 



The physical characters of the flow of fluids were briefly 

 described by the example of water in an open stream. 

 A stream might well up from a spring in a flat country, 

 and swim with very low pressure to its mouth ; or, falling 

 from a inountain, might have pressure enough to carry 

 men and horses off their legs. If the volume were also 

 great, as in the sea, it might e.xercise a pressure of many 

 tons to the square yard, and smash great bulwarks to 

 pieces. But in the higher animals the blood flows in 

 closed channels, so that in such a scheme as theirs the 

 dimensions of the channels assume a very important value.. 

 Moreover, in mammalia the circulating fluid is not water, 

 but a thicker fluid — the blood — which (in man) has at least 

 four times the viscosity of water. The enormous value of 

 friction in the circulation was then considered, and it was 

 .shown that in this factor the kind of vessel wall does not 

 signify much, as the wall is lined by a practically stationary 

 layer of the fluid ; friction, therefore, which uses up 

 99/iooths of the heart's power, depends on the factor of 

 viscosity together with that of the dimension of the 

 channels, or closed bed. It may be said that the blood 

 pressures — that is, the arterial pressures — in man depend 

 on viscosity and dimension of stream bed. 



Now so far the closed tubes had been regarded as rigid. 

 But if in animals the tubes were rigid the circulation 

 would be carried on under great difficulties. For instance, 

 there would be no accommodation ; only so much blood 

 could be driven into the system as issued at the periphery ; 

 the stream, too, would be quite intermittent, with very 

 high maximum and very low minimum pressures, which 

 would not serve for continuous nutrition, and bv its e.x- 

 tremes of pressures would soon wear down the arteries. For 

 instance, in the bagpipes, were it not for the air reservoir 

 the sound would issue in spasmodic screams ; whereas the 

 air-bag turns the intermittent blowing into a continuous 

 feed of air. In the arterial system of man the same pro- 

 vision is made ; its tubing is highly elastic, and a chief 

 part of it — namely, the aorta — being' relatively wider than 

 other branches of the tree, contains, like the bagpipe 

 reservoir, accommodation for very variable supplies of 

 output from the heart pump. Thus a very large part of 

 the heart power is used in dilatation of the vessels, and 

 by these is given back to the blood. The valves of the 

 heart serve a like purpose of regulating the pressure of the 

 supply to the vascular system. 



1 Abstract of a lecture delivered by Prof. T. Clifford Allbutt, F.R.S., at 

 the Roy.il Institution on February 3. 



NO. 1842, VOL. 71] 



I he lecturer in the next place dealt with the pulse, 

 contrastmg the travel of the wave with the travel of the 

 blood Itself. The wave due to the shock of the heart beat 

 travels, ordinarily, about twentv times as fast as a given 

 particle of the blood itself. The tenser the walls of the 

 arteries the faster the wave travels along the taut vessels, 

 but the slower the passage of the blood itself. Herein lies 

 one of the chief evils of a morbid rise of arterial pressure ; 

 more stress on the vessels, less distribution of their contents. 

 Many of these processes were illustrated by lantern slides and 

 demonstrations by Dr. Dixon, demonstrator of pharmacology 

 in Cambridge. 



After these principles Dr. Dixon exhibited the various 

 instruments in use for measuring blood pressures in man, 

 and the means by which their curves may be recorded on a 

 revolving drum (1-cymograph). 



The lecturer then entered upon the vital properties of 

 the arteries — that they are not only elastic, and so ac- 

 commodate themselves to the varying pressures, but are 

 endowed also with nervous governance, whereby they effect 

 a large economy in work and material. Several functions 

 of the human body cannot, save within small limits, work 

 together. If we are digesting we are not apt for thought ; 

 the Alpine climber is mercifully unable to worry over affairs 

 — his mind is put into abeyance ; and so on. Thus the 

 arterial system, by the means of its nervous connections, 

 contracting in some areas and dilating in others, 

 automatically diverts its fertilising streams hither or 

 thither as needs arise. Moreover, it can enlarge or 

 diminish its bed according to the total quantities of blood 

 temporarily in circulation — a quantity which is very vari- 

 able. By contracting the arteries in considerable areas 

 and correspondingly dilating them in others, the fields of 

 the various functions of the body can be used alternately, as 

 we see in the irrigation of .Mpine meadows. By the same 

 means the very various pressures of the blood can be 

 counteracted. When under muscular effort, for instance, 

 the pressure is raised, a corresponding area outside the 

 muscles is dilated, and pressure more or less equalised ; thus 

 the heart is enabled to do the most work with the least dis- 

 turbance of stresses. So in a bath, cold or very hot, the 

 crimping up of the large cutaneous areas is compensated 

 by large dilatations in internal areas, and pressures return to 

 the normal in two or three minutes. The chief area in which 

 blood can be accommodated, and thus for a time put out of 

 circulation, is a large abdominal area. 



By these considerations the lecturer was led to explain why 

 the blood in the body does not drop down into our feet and 

 legs, and leave the brain and other vital parts. Indeed, 

 the blood has a strong disposition thus to obey the action 

 of gravitation, and one of the events of approaching death 

 is the falling of the blood into lower parts of the body, 

 deserting the heart and brain. Obviously this is especially 

 the case in upright animals, as in man chieflv, and in apes 

 in some measure. It is by the vigilance of the nervous 

 governance that the blood is held up, by the contraction of 

 the abdominal vascular fields ; and it is the failure of these 

 mechanisms which appears as shock, syncope, or collapse. 

 The lecturer, assisted by demonstrations by Dr. Dixon, 

 illustrated these dispositions, citing especially the researches 

 of Prof. Leonard Hill on the distribution of the blood in 

 various positions of the body. He also referred to the 

 bearing of these principles on the researches of Prof. 

 Waller and others on the dangers of anaesthetics. By some 

 most interesting experiments by Dr. Cushing he showed 

 how enormously the arterial pressures may be raised in 

 case of danger of failure of supply of blood against gravity 

 when, as in apoplexy or a depressed fracture of the skull, the 

 blood-vessels, in the parts of the brain where all these 

 mechanisms find their centres, are compressed and thus more 

 or less liable to be emptied. 



In the last part of the lecture the lecturer apologised for 

 occupying time with so much physiology, in which subject 

 he is not an investigator. But it was necessary to make 

 manifest to his audience how great is the importance of the 

 integrity of the arteries themselves, and of their nervous 

 governance in function, an integrity which is a matter of life 

 and death ; for if the circulation fails in the nervous centres 

 or heart, life must cease. Now the arteries are subject to 

 many injurious conditions, as of certain poisons and infec- 



