Peyer, Johann Conrad

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(b. Schaffhausen, Switwerland, 26 December 1653; d. Schaffhausen, 29 February 1712)


Born into a patrician family, Peyer studied medicine in Basel before becoming the pupil of J. Guichard du Verney at Paris and later of Vieussens at Montpellier. He then returned to his native Schaffhausen, where, with his teacher Johann Jakob Wepfer and the latter’s son-in-law Johann Conrad Brunner, he formed the“Schaffhausen trio,” whose important contributions to the new methodology of medical research were the explanation of symptoms by connecting them with the lesion in the body, considered as the site of the disease, and experimentation on animals (anatomia animata) to study either the functioning of organs or the effects of medicines on the organism. It is not always easy to determine the individual contribution of each member of the trio from their joint publications. In any case, after a ten-year collaboration through the 1680’s Peyer quarreled with Wepfer and Brunner and spent the rest of his life as professor of logic, rhetoric, and medicine at the local Gymnasium.

A member of the Academia Naturae Curiosorum Sacra, Peyser sent, under the pseudonym Pythagoras, many letters to the Academy on the antiperistaltic movements of the intestine, cinchona bark, and other subjects.

The iatrochemical theories that were then dominant oriented scientists toward the study of digestion and the digestive system. Hence in 1682 Peyer described the lymphatic nodules and masses located in the walls of the ileum that now bear his name (or sometimes that of Johannes Nicolaus Pechlin, who in 1672 had described them in a work on the anatomy of the intestinal tract). According to William Cole, Severino had observed follicular regions in the small intestine of animals (1645).

Adenography was then in fashion, but the interpretation of the dissections is somewhat confusing today. In fact, the chemical phenomena of digestion were unknown, and the theory of the lymphatic system had barely been outlined. It was thought that the excretory canal of the pancreas was a chyliferous vessel originating in the intestine and entering the gland (Moritz Hofmann, 1641; J. G. Wirsung, 1642). C. Brunner attributed to the duodenal glands that now bear his name a role in the secretion of lymph. Thus it is not astonishing that Peyer supposed the ileal follicles to be glands excreting the digestive juices (E. Hintzsche, pp.2401-2402).

Peyer also studied the stomach of ruminants in his Merycologia (1685) and the anatomy of normal and abnormal fetuses. He probably assisted Brunner in his pancreatecdtomies on dogs. These operations resulted in diabetes, but neither Peyer nor Brunner could interpret the results obtained (1683).

Wepfer—apparently the leader of the Schaffhausen trio—had written the first book on experimental toxicology, Cicutae aquaticae historia et noxae commentario illustrata (1679). He had been led to believe that the activity of the heart could be explained only by its special structure. Peyer attempted to confirm this hypothesis, either with his Schaffhausen friends or with his Basel friend J. J. Harder. In 1681 he succeeded in making the hearts of dead animals—and even of human beings who had been hanged—beat by blowing air into the veins or by utilizing other stimuli. Despite his imperfect technique he achieved an artificial cardiac activity lasting several hours. These experiments were repeated in 1702 by Baglivi, who studied the tonicity of the fibra motrix. He concluded from them that the heart died not from lack of nervous fluid but from lack of blood (M. D. Grmek, pp. 313-314). Later, supporters of the doctrine of irritability investigated this problem, taken up by Bidder. In his letters to Harder, Peyer revealed some of his other discoveries: hermaphroditism of the pulmonate snail and an epizootic disease that may have been foot-and-mouth disease.


I. Original Works. Peyer’s writings include Exercitatio anatomico-medica de glandulis intestinorum, earumque usu et affectionibus. Cui subjungitur anatome ventriculi gallinacei (Schaffhausen, 1677); Methods histroiarum anatomico-medicarum exemplo ascitis vitalium oirganorum vitio ex poericardii coalitu cum corde nato illustrata (Paris, 1678); Mediatatio de valetudine humana (Basel, 1681);Parerga anatomica et medica septem (Geneva,1681); Paeonis et Pythagorae exercitationes anatomicae et medicae familiares bis quinquaginta, Hecatombe non Hecatae sed illustri Academiae naturae curiosorum sacra (Basel,1682), 100letters dated 12 Jan.1677 to 8 July 1681written by Peyer (Ppythagoras)and Harder (Paeonis);Merycologia sive de ruminantibus et ruminatione commentarius (Basel, 1685); and Observatio circa urachum in foetu humano pervium edited by his son Johan JacobPeyer (Lyons, 1721).

II. Secondary Literature. See E-H.Ackerknecht, Grands medecins suises de 1500 a 1900, conference du Palais de la Decouverte D109 (Paris, 1966);Conrad Brunner and Wilhelm von Muralt, Aus den Briefen hervorragender schweizer Ärzte des 17. Jahrhunderts (Basel, 1919), 153–226; M. D. Grmek, “La notion de fibre vivante chez les medecins de l’école iatrophysique,” in Clio medica, 5, no. 4 (Dec. 1970), 297–318; E. Hintzsche, “Anatomia animata,” in Revue Ciba, 69 (1948), 2395–2412; Recherches, decouveertes et inventions des medecins suisses (Basel, n.d.); Robert Lang, Das Collegium humanitatis in Schaffhausen I,1648-1727 (Leipzig, 1893),29ff;F.V.Mandach,“ Uber das klassische Werk des schweizer Arztes Joh. Conr Peyer De glandulis intestinorum in Korrespondenzblatt für schweizer Ärzte, 33 (1903), 445–450, 479–482; Bernhard Peyer and Heinrich Peyer, “Bildnis und Siegel des Arztes Johann Conrad Peyer,” supp. to Veröffentlichungen der Schweizerischen Gesellschaft für Geschichte der Medizin..13 (1903),445-450, 479-482; Bernhard Peyer-Amsier, “Johann Conrad Peyer 1653-1712,” in Reinhard Frauenfelder, ed., Geschichte der Familie Peyer’s mil den Wecken 1410-1932 (Zurich, 1932), 299-346-notes 1-7, pp. 333 F., list all the works dealing with Peyer’s life and there is a facs. of a letter by Peyer on p. 323 (note [1] on Peyer also appeared as a supp. to Veroffentlichungen der Schweizerischen Gesellschaft für Geschichte der Medizin8 [1932]); and H.E. Sigerist,“Die Verdienste zweier Schaff hauser Arzte (J.C,Peyer and J.C.Brunner)um die Erforschung der Darmdrusen,” in Verhandlungen der Schweizerschen naturforschenden Gesellschaft102 (1921). 153 f.

Pierre Huard
M. J. Imbault-Huart