372 



SCIENCE 



[N. S. Vol. XLIV. No. 1133 



niss des Binflusses der Respirationsbeweg- 

 imgen auf den Blut lauf in Arteriensys- 

 tems," published in Mutter's ArcJiiv, 1847. 

 "To obtain reliable figures under all cir- 

 cumstances by means of it (referring to 

 Poiseulle's mercury manometer), and at 

 the same time, time determinations for the 

 duration and course of the different pres- 

 sures, one places a rod-like float on the 

 mercury, puts on the upper end a writing- 

 point, and lets it draw the variations in 

 pressure on a surface, which moves by the 

 pointer with a constant velocity. In this 

 way one obtains curves, the height of which 

 is a measure of the blood pressure, and 

 the width an indication of the time." 

 Ludwig recorded the movements of the 

 respiration and the oscillations of the 

 blood pressure on the same paper simulta- 

 neously, and thus obtained curves which 

 made possible an accurate comparison of 

 the two series of events. 



Although the graphic method was known 

 at the beginning of the century to meteorol- 

 ogists and physicists (especially through 

 the work of Thomas Young), it had been 

 neglected and was carried again into phys- 

 ics and meteorology after the discovery of 

 the kymographion. It has become, with its 

 many modifications, an indispensable aid 

 to the physiologist, pharmacologist, pathol- 

 ogist, clinician, and to experimental biol- 

 ogists and botanists. His pupil Angelo 

 Mosso, the celebrated Italian physiologist, 

 showed me the original tracing when I 

 visited his laboratory in Turin. There is 

 inscribed upon it the date, December 12, 

 1846, and notes concerning the experiment. 

 It was the first time that the heart and 

 respiration had spoken in their own lan- 

 guage, and Ludwig in presenting it to 

 Mosso wrote on the back — "I give to my 

 friend Mosso for his collection, this first 

 stammering of the heart and of the chest." 



This was followed by researches into the 



structure and changes in form of the beat- 

 ing heart, which served to explain the true 

 significance of the apex beat. He also did 

 much to increase our knowledge of the 

 cause of the first sound of the heart. All of 

 these studies on the mechanics of the cir- 

 culation naturally led Ludwig, to a consid- 

 eration of the means by which it is regu- 

 lated, and so to a study of the nerves which 

 act on the circulatory system. 



The "Weber brothers had discovered the 

 effect of the vagus nerve to inhibit the 

 heart. Schmiederberg, under Ludwig 's 

 guidance, 1866, discovered the accelerator 

 nerve of the heart of the frog and of the 

 dog, and in 1883, Wooldrich found centrif- 

 ugal fibers to the heart of the dog, which 

 altered the blood pressure without chang- 

 ing the rate of the beat. Bowditch, the 

 best known of American physiologists, 

 Luciani and Stienon, studied the effects of 

 electrical excitations on the heart muscle, 

 and ascertained a number of facts of theo- 

 retical importance to heart and muscle 

 physiology. 



Henle had observed the muscles in the 

 walls of the blood vessels and Claude Ber- 

 nard the existence of nerves which cause 

 the constriction of certain blood vessels. It 

 was left for Ludwig and Thiery to point 

 out, 1863, the importance of these nerves 

 in maintaining the tonus of the blood 

 vessels, and consequently the blood pres- 

 sure. Cutting the spinal cord was found to 

 cause a fall, and exciting it a rise of blood 

 pressure, without any change in the rate of 

 the heart. They saw the vessels of the 

 abdomen contract, and thought that the 

 nerves ran in the splanchnic, a fact which 

 Ludwig and Cyon proved in 1866. More- 

 over, during these latter experiments a 

 nerve was found which ran from the heart 

 to the medulla, the depressor nerve, which 

 acts reflexly from the heart to dilate the 

 blood vessels, and which protects the heart 



