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SCIENCE 



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



an iron hook which we needed. I bent one 

 which I thought would do, but without 

 criticizing it directly, he proceeded, while 

 discussing the work, to painstakingly re- 

 bend it, until it exactly fitted our need. I 

 carried that hook in my pocket for years, 

 and although I finally lost it, the lesson has 

 clung. 



He taught his students independence. 

 On one occasion when I offered to help him 

 tie a ligature in a difficult place, he said 

 with a merry smile, "No, no; if I let you 

 help me now, you will want me to come 

 and help you the next time you have a 

 knot to tie." 



Kronecker said of him : 



He understood how to instil his ideas so that 

 those working under him often thought them their 

 own. But he wished to bring out his own charac- 

 teristic methods of expression when it came to the 

 publication of the work, and every expert was able 

 to recognize in the papers coming from the Leip- 

 zig institute the hidden thoughtful exposition of 

 the master. 



Von Frey admirably described his char- 

 acteristics when he wrote, 



The steadfastness with which Ludwig clung to 

 the complete control of the direction of the work, 

 might suggest a form of military discipline in the 

 laboratory. This certainly did not apply to the 

 personal relations which existed. Nevertheless, 

 such a comparison is not without value for an 

 understanding of the exceptional results of his 

 teaching. Among other qualities Ludwig pos- 

 sessed those which could be described as marked 

 mili tary virtues: boldness of design, tenacious 

 perseverance in execution, presence of mind and 

 high personal courage, an unusual talent for or- 

 ganization bound up with a knowledge of men, 

 which knew how to put every force in its right 

 place, strict discipline, frankness and heartiness in 

 personal relations, indefatigableness in work, to- 

 gether with exemplary orderliness and punctuality. 



With the love which our master inspired, 

 there developed in the laboratory an esprit 

 de corps, so that to have worked with him 

 was a password that gave free entrance 

 to the laboratory and the friendship of 

 every other who had been his pupil. 



Ludwig 's old students, in token of their 

 esteem, on the occasion of his twenty-fifth 

 anniversary as ordentlicher professor, pre- 

 sented him with a Festschrift. In this was 

 a list of his pupils up to that time, which 

 numbered 142. In the twenty years that 

 followed, a hundred others worked with 

 him. 



Many of Ludwig 's researches were 

 purely anatomical, or the physiological 

 problems were handled chiefly on an ana- 

 tomical basis. One thinks of the structure 

 of the heart and its relation to its change 

 of form, and of his attempts to bring the 

 structure and course of the blood vessels in 

 various organs into the explanation of 

 their function. The excellent methods of 

 injection of blood vessels developed in his 

 laboratory, made it possible for him to 

 study the circulation in many organs as it 

 had never been done before, e. g., in the 

 eye, ear drum, liver, lymph glands, corpora 

 cavernosa, intestines, muscle, ear-labyrinth, 

 larynx, skin. Especially worthy of men- 

 tion is the natural injection of the lymph 

 spaces, by means of which Schweiger- 

 Seidel and Ludwig studied the lymphatics 

 of the pleura, the central tendon of the 

 diaphragm, the retina and the liver. 



As far as is known, his first physiolog- 

 ical research was his habilitationsschrift, 

 "Beitrage zur Mechanismus der Harnse- 

 cretion," published in Marburg, 1842, 

 when he was twenty-five years old. In this 

 work on secretion by the kidney, he de- 

 veloped the first physical theory of secre- 

 tion of a gland. He deduced the method 

 of the secretion of the urine from the struc- 

 ture of the kidney, and the physical forces 

 which he thought must necessarily control 

 them. 



This work made him desire to know more 

 concerning the action of physical forces on 

 the passage of fluids through animal mem- 

 branes, and led to important researches on 



