CARL LUDWIG. 167 



chest-wall, the rapid movements of the heart, and the blood 

 pressure. Thus was opened up a new and fertile field of 

 study. Since then in all sciences the graphic method 

 has played an essential part. On its applications to 

 physiology, Marey, Professor in the College de France 

 at Paris, has written a whole book, and he himself has 

 greatly extended our knowledge of technical appliances for 

 this purpose. Ludwig published his results in M tiller's 

 Arckiv, pp. 240-302, 1847, " Beitrage zur Kenntniss d. 

 Einflusses d. Respirations- Bewegungen a. d. Blutlauf im 

 Aortensystem ". 



To a dearly loved and much esteemed pupil, Professor 

 Angelo Mosso of Turin, Ludwig presented the original 

 tracing which was published in Miiller's Arckiv with the 

 characteristic dedication on the back of the tracing, written 

 in the neat crisp characters for which Ludwig was famous, 

 " Der Sammlung des Freundes Mosso stiftet dieses erste 

 Stammeln des Herzens und der Brust. C. Ludwig, Leipzig, 

 1 5th August, 1 874." On the front of the tracing was the date 

 xii., 1846. It is obvious that the Kymograph, apart from 

 its intrinsic importance in the laboratory, is the forerunner 

 of the innumerable applications of the graphic method. To 

 record one tithe of the results won by this instrument or its 

 descendants would be to record the progress of the physio- 

 logy of the vascular system during the last half-century. 



Confining our attention for the present to the heart, in 

 vol. i. of the Arbeiten, issued in 1867, we have a description 

 of a very remarkable nerve. In the neck of the rabbit and 

 some other animals there is a small isolated nerve, a branch 

 of the vagus nerve in the neck, which pursues an indepen- 

 dent course and runs to the heart, or, speaking physio- 

 logically, proceeds from the heart, to join the vagus, and is 

 carried above the larynx in this nerve-trunk to join the 

 medulla oblongata or bulb. This nerve was discovered by 

 Ludwig and Cyon, and was named by them the "depressor" 

 nerve. Why? They found that when this nerve was divided 

 and its central end stimulated, the blood pressure in an 

 artery being recorded simultaneously by means of the 

 Kymograph just described, after a few seconds there was a 



