Rudolf Peter Heinrich Heidenhain

Rudolf Peter Heinrich Heidenhain has a special position among the physiologists of the second half of the nineteenth century. He was an independent worker and thinker not influenced by, and often opposed to, the modish currents of the time, especially to the tendency of oversimplification in the explanation of vital phenomena and to the effort to reduce them to fairly simple physical and chemical processes. He was oriented more toward biological conceptions of vital phenomena than to their mathematical and physical interpretation. He did not trust preconceived opinions or theories, relying instead on the results of his experiments and on the inductive method.

A doctor at 20
Heidenhain was the eldest of twenty-two children of the physician Kreisphysikus Heinrich Jacob Heidenhain (1808-1868). He very early revealed his talent and perseverance in work; his diligence in collecting plants and animals indicated his interest in the study of nature. After he completed his secondary education in his native town at the age of sixteen, he began the study of nature on an estate near his home but soon turned to medicine at the University of Königsberg; in this he was guided by his father, who had great influence on his early work and decisions.

It was fairly common in Germany to attend several universities for undergraduate study, so Heidenhain went after two years to Halle, where Alfred Wilhelm Volkmann (1801-1877), one of the leading German physiologists of his time, tuned his interest to physiology. After another two years he went to Berlin, where he finished his medical studies at the astonishing early age of twenty years with a doctoral dissertation entitled De nervis organisque centralibus cordis, cordiumque lymphaticarum ranae (1854), which had been inspired by Emil du Bois-Reymond (1818-1896).

In his dissertation Heidenhain refuted the opinion advanced by Moritz Schiff (1823-1896) that the vagus nerve initiates the rhythmic contractions of the heart, demonstrating in his experiments that its functions is to regulate heart activity; the automatic activity seemed to him to originate in the ganglia of the heart. Heidenhain remained with du Bois-Reymond at Berlin, working on the problem of the tonus of skeletal muscles and some other questions of nerve and muscle physiology. The results were published in Physiologische Studien (Berlin, 1856).

Herr Professor – at 25
In 1856 Heidenhain returned to Volkmann’s laboratory in Halle. The following year he submitted a Habilitationsschrift on the determination of the blood volume in the bodies of animals and men, improving on Hermann Welcker’s method (1822-1897). He married Volkmann’s daughter Fanny in January 1859, shortly before he assumed the chair of physiology at Breslau. Students at first revolted against the «unknown and green young professor,» and some older professors also showed their resentment: "One cannot have much respect for the discipline which can be represented by a twenty-five year-old teacher and master.» Nevertheless, through his diligence and competence, Heidenhain soon won respect and became one of the most illustrious members of the Breslau Medical Faculty, where he broadened his research activity and maintained it almost until his death in 1897.

The hot beats of the heart
In Breslau Heidenhain continued his work on muscle and nerve, still under the influence of du Bois-Reymond. His most important accomplishment was the measurement of heat production during muscle activity. Although production of heat during a longer tetanic contraction had been found since 1805 by several observers, Heidenhain was the first to detect, by sensitive thermoelectric measurement, a minute increase in temperature - 0.001-0.005°C. - during every simple twitch.

His most important finding was that the total energy output (heat and mechanical work) increases with increasing load (increasing active tension), an unexpected result. It showed that muscle liberated more energy when the resistance to its contraction was greater - that there is a kind of self-regulation of the energy expenditure in the working muscle - and thus that the muscle’s work is very economical. When fatigue sets in, the work becomes even more economical. Thermoelectric measurement has since become an important and widely used research tool in muscle physiology, for which Heidenhain’s classic work helped to form a basis.

Other research
Among Heidenhain’s other important findings in muscle and nerve physiology were that of increased acid formation in the working muscle and that of special motor reactions produced by stimulation of the motor nerve (1883), the so-called speedometer phenomenon, which was not explained until much later.

In 1867 Heidenhain began systematic studies of the physiology of glands and of the secretory and absorption process, which remained his chief field of interest for the rest of his life. He noticed in the stomach two types of calls in the gastric glands and showed that one secrets the enzyme pepsin, the other hydrochloric acid. He worked out a method of a «small stomach» or gastric pouch, later improved by Ivan Petrovich Pavlov (1849-1936), who worked for some time in Heidenhain’s laboratory and always held Heidenhain in great esteem. The Heidenhain pouch was similar to the Pavlov pouch but with the vagal nerves severed. The gastric pouch technique has been widely used in several modified forms and has proved extremely useful in the investigation of gastric secretion and its regulations. Carl Weigert (1845-1904) was influenced by Heidenhain when he studied medicine in Breslau. Heidenhain also conducted experiments on hypnotism, trying to study the phenomenon of "animal magnetism" scientifically.

Heidenhain had the title of privy medical counsellor – Geheimer Medizinalrath.

• De nervis organisque centralibus cordis cordium-que ranae lymphaticorum. Doctoral dissertation, 1854.
• Disquisitiones criticae et experimentales de quantitate sanguinis in corpore mammalium exstantis. Habilitation thesis. Halle, 1857.
• Physiologische Studien. Berlin, 1856.
• Mechanische Leistung; Wärmeentwicklung und Stoffumsatz bei der Muskelthätigkeit. Leipzig, 1864.
• Beiträge zur Lehre von der Speichelsecretion.
  Studien des Physiologischen Institutes zu Breslau, 1868, 4: 1-124.
• Der sogenannte thierische Magnetismus. Physiologische Beobachtungen. Leipzig, 1879.
• Ueber die Wirkung einiger Gifte auf die Nerven der glandula submaxillaris.
  [Pflüger’s] Archiv für die gesamte Physiologie des Menschen und der Tiere, 1872, 5: 309-318.
  Study on the effect of poisons on the nerves of the submaxillary gland.
• Versuche über den Vorgang der Harnabsonderung. [Pflüger’s] Archiv für die gesamte Physiologie des Menschen und der Tiere, 1874, 9: 1-27.
  Heidenhain's "secretion" theory of renal function.
• Ueber secretorische und trophische Drüsennerven. [Pflüger’s] Archiv für die gesamte Physiologie des Menschen und der Tiere, 1878, 17: 1-67.
  Investigation of the secretory and trophic nerves of glands. Heidenhain considered all secretory phenomena to be intracellular, rather than mechanical, processes.
• Die Vivisektion im Dienste der Heilkunde. Leipzig, 1879.
• Physiologie der Absonderungsvorgänge.
  In: Ludimar Hermann (1838-1914) et al: Handbuch der Physiologie; volume V; Leipzig, 1880.
• Versuche und Fragen zur Lehre von der Lymphbildung.
  [Pflüger’s] Archiv für die gesamte Physiologie des Menschen und der Tiere, 49.
• Neue Versuche über die Aufsaugung im Dünndarm. [Pflüger’s] Archiv für die gesamte Physiologie des Menschen und der Tiere, 1894, 56: 579-631.
• Beiträge zur Histologie und Physiologie der Dünndarmschleimhaut.
  [Pflüger’s] Archiv für die gesamte Physiologie des Menschen und der Tiere, Berlin, 43, Supplement. Heidenhain’s papers were published first in the collection Physiologische Studien (Berlin, 1856), then in the series Studien des Physiologischen Institutes zu Breslau, 4 pts (Leipzig, 1861-1868), and the rest mostly in [Pflüger’s] Archiv für die gesamte Physiologie des Menschen und der Tiere.
• Herbert Broghammer:
  Experimentelle Physiologie und mikroskopische Anatomie in der Nachromantik : Rudolf Peter Heinrich Heidenhain (1834 - 1897).
  Aachen : Shaker Verlag GmbH, December, 2000. Paperback, 199 pages.