October 25, 1894 J 



NATURE 



627 



Sanderson and Michael Foster, under the auspices of 

 Acland and Humphrey, have diffused amongst the 

 medical men of this country a knowledge of physiology so 

 extensive and exact as could only be found, before their time, 

 amongst those who had made a special study of the subject. 

 Yet more than to them, more than to anyone else since the time 

 of Harvey, do we owe our present knowledge of the circulation 

 to Carl Ludwig. He it is who first enabled the pressure of 

 blood in the arteries to record its own variations automatically, 

 so that alterations could be noticed and measured which were 

 too rapid or too slight to be detected by the eye. To him, 

 also, we owe the plan of artificial circulation by which the changes 

 in the functions of the organs and in the vessels which 

 supply them can be observed, quite apart from the heart, lungs, 

 or from the nervous system. 



Like Sharpey, Ludwig is a great teacher, and like the great 

 architects of the Middle Ages, who built the wonderful cathe- 

 drals which all admire, and the builder of which no man 

 knows, Ludwig has been content to sink his own name in his 

 anxiety for the progress of his work, and in his desire to aid his 

 pupils. The researches which have appeared under these 

 pupils' names have been in many instances, perhaps 

 in most, not only suggested by Ludwig, but carried out experi- 

 mentally with his own hands, and the paper which recorded 

 the results finally written by himself. In the papers which 

 have appeared under his pupils' names we find their obli- 

 gations to the master recorded in such terms as ' unter 

 Mitwirkung." But no one, except those who have worked 

 with him, can understand what such co-operation meant. 



The graphic method introduced by Ludwig for the purpose 

 of measuring the blood pressure, was adapted by Volkmann to 

 the registration of the pulse in man, and the same method has 

 been modified and rendered more easily applicable at the bed- 

 side by Marey and Chauveau, to whom we chiefly owe our 

 knowledge of the modifications in the form of the apex beat, 

 and of the pulse curve. It is to Ludwig and his scholars, how- 

 ever, that we owe the greater part of our knowledge of the 

 mechanism of the circulation, and of the varying distribution 

 the blood in various parts of the body. 



The effect of emo'ion upon the heart was carefully noted by 

 Harvey, who says : " For every affection of the mind which is 

 attended wiih pain or pleasure, hope or fear is the cause of an 

 agitation whose influence extends to the heart." ' 



Not only was Harvey well acquainted with the fact that the 

 beats of the heart vary very mach in strength and force, but he 

 also knew that the circulation in various parts of the body may 

 be very different at one and the same time. He says : "It is 

 manifest that the blood in its cour.se does not everywhere pass 

 with the same celerity, neither with the same force in all places, 

 and at all times, but that it varies greatly according to age, sex, 

 temperament, habit of body, and other contingent circum- 

 stances, external as well as internal, natural or nou-natural. 

 For it does not course through intricate and obstructed passages 

 with the same readiness that it does through straight, unimpeded 

 and pervious channels. Neither does it run through close, hard, 

 and crowded parts, with the same velocity as through spongy, 

 soft, and permeable tissues. Neither does it flow and penetrate 

 with such swiftness when the impulse (of the heart) is slow and 

 weak, as when this is forcible and frequent, in which case the 

 blood is driven onwards with vigour, and in large quantity." 



•* And what, indeed, is more deserving of attention than the 

 fact that in almost every affection, appetite, hope, or fear, our 

 body suffers, the countenance changes, and the blood appears to 

 course hither and thither. In anger the eyes are fiery and the 

 pupils contracted ; in modesty the cheeks are suffused with 

 blushes ; in fear, and undera sense of infamy and of shame, the 

 face is pale, hut the ears burn as if for the evil they heard or 

 were to hear ; in lust, how quickly is the member distended with 

 blood and erected." - 



Harvey's great contemporary, Milton, though so violently 

 opposed to him in politics, would certainly not remain in 

 ignorance of Harvey's work, and he has noted the changes 

 in the colour of the face produced by emotions. In describing 

 the behaviour of Satan on his journey from Hell to Paradise, he 

 says : — 



"Thu5 while lie spake, each passion ditnm'd_hi.s face, 

 Thrice changed with pale— ire envy, and despair ; 

 Whicll marr*d his horrow'd visage." •* 



» •■ The Works of William Harvey," Sydenham Society's edition, p. 70. 



2 Ibid.t p. i2S-t29 



* " Paradise Lost," by John Milton, Book iv., p. 85. 



But although these fac!s were known to Harvey so long ago, 

 it is only in comparatively recent years that the mechanism by 

 which they are brought about has been investigated, and it is 

 only within the last dejade that physiologists have begun regu- 

 larly to believe that the cardiac muscle has a power of rhythmic 

 pulsation independent of its nerves, although Harvey had noted 

 that when the heart was cut into small pieces the fragments 

 would still continue to pulsate. We may fairly, indeed, com- 

 pare the movements of the heart, as regarded by physiologists 

 of the present day, to those of a horse which is capable of going 

 independently, although its pace may be slowed or accelerated 

 by the reins or spur of the rider. The power of the vagus to act 

 as a rein to the heart, and slow its movements, or stop them alto- 

 gether, was first noted by Edward and Ernest Heinrich Weber, 

 while the effect that it sometimes has of accelerating instead of 

 slowing, like the effect of shaking the reins of the horse, 

 was observed by Schiff, Moleschott, and Lister. 



The accelerating nerves of the heart, and the position of the 

 nerve-centre from which 'hey spring, were more thoroughly in- 

 vestigated by von Bezold,' while the power of the vagus to 

 weaken as well as slow the heart was observed by Gaskell. The 

 position of the cardiac centre, which, like the rider, regulates 

 the movements of the heart, was located in the medulla 

 oblongata chiefly by Ludwig and his scholars. Like the 

 heart, the vessels also are regulated in diameter by the nervous 

 system in accordance with the wants of the b3dy generally ; and 

 the effect upon the vaso motor nerves which, when cut, allow 

 them to dilate, and when stimulated cause them to contract, was 

 discovered by Bernard, Brown-Sequard, and by our countryman. 

 Waller ; while the power of other nerve; to cause immediate 

 dilatation was discovered by Bernard, Eckhardt, and Ludwig 

 in the submaxillary glands, penis, and peripheral vessels 

 respectively. 



The heart, when cut out of the body, still continues 

 to beat, and the transmission of excitation from one 

 cavity to another was experimented on by Paget, although 

 removed completely from the influence of the central ner- 

 vous system, and the vessels have a somewhat similar power 

 of independent contractility. The alterations produced in 

 the circulation generally and locally by the contractile power of 

 the vessels, and the changes caused in the vessels by the 

 central nervous system, by peripheral stimulation of the nerves, 

 or by variations in the quality of the blood, have formed the 

 subject of a series of researches extending over many years ; 

 and though originated, and in many cases entirely conducted, by 

 Ludwig, have appeared to a great extent under the names of 

 his pupils. The starting-point of these investigations was an 

 examination of the changes in the blood as it flowed through 

 isolated organs, with the view of ascertaining in what manner 

 the combustion by which the animal heat is maintained was_ 

 effected in the body. While keeping up the circulation of 

 blood through the vessels of muscles severed from the body, 

 Ludwig and Sczelkow - observed variations in the flow which 

 appeared to indicate contractile power in the vessels themselves. 

 This research was carried on under Ludwig's direction by 

 various of his scholars in succession, Alexander Schmidt, 

 Dogiel, Sadler, myself, Hafiz, Lepine, A. Mosso, von Frey, 

 and Gaskell. Their observations, as well as those of Cohnheim 

 and Gunning, have shown that the muscular fibres of the 

 arterioles, not only in the muscles but throughout the body 

 generally, have a power of independent and sometimes 

 rhythmical contraction and relaxation. Their contractility is, 

 however, controlled by the central nervous system in accord- 

 ance with the wants of the body generally. For the amount of 

 blood contained in the body is insufficient to fill the whole of 

 the vascular system at once ; and when the vessels are fully 

 dilated, as they are after death, we find that nearly the whole 

 of the blood of the body may be contained in the veins alone. 

 It is, therefore, necessary that when one part of the body is 

 receiving a larger supply of blood, another should be receiving 

 a smaller supply ; and the funclions of the vaso moior centres 

 have been well compared by Ludwig to the turncocks in a 

 great city, who cut off the water supply from one district at the 

 same time they turn it on to another. Thus it is that when the 

 brain is active the feet may get cold, and Mosso has shown this 

 in an exceedingly neat manner by placing a man on a large 

 board delicately balanced at its centre, and demonstrating that 



' Von Beiold " Untersuchungen uberdielnnervationdes Hcnens," 1863. 

 L.eipziK : tngelmann. . „^ .^ ,.,.,..«, , 



-Ludwig and Sczelkow. "Henleand Pfcuffers Zeit.schrift, 1863, vol. 17. 

 p. it^ and viiic p. 122. 



NO, 1304, VOL. 50] 



