PEZARD, ALBERT

(b. Neuflize, Ardennes, France, 1 April 1875; d. Paris, France, 21 November 1927)

endocrinology.

Pezard’s parents were farmers. He studied at the Ecole Normale of Charleville, then won admission to the Ecole Normale of St.-Cloud. Several professors from the Sorbonne who taught at St.-Cloud soon found that Pezard was one of their most brilliant science students. He obtained his master’s degree from the University of Paris with honors in both physical and natural sciences. His success in the difficult natural sciences agregation made him eligible for a professorship at two renowned Paris colleges: Colbert and Jean-Baptiste Say. Pezard’s teaching duties were time-consuming but he fulfilled them even after 1908, when he was active in biological investigation. His attraction to research was noticed by one of his former teachers at St.-Cloud, Charles Gravier, professor of zoology at the Museum d’Histoire Naturelle, who recommended him to Emile Gley, professor at the College de France, one of the founders of endocrinology. Gley directed the Station Physiologique du College de France, and Pezard was soon elected associate director of the station, where he worked for nearly twenty years.

Pezard first studied the physiological conditioning of the secondary sexual characters in birds. Full publication of his findings, in his doctoral dissertation, was delayed until 1918 by his military duties during World War I. The dissertation contained many new results, such as Pezard’s establishment of the true secondary sexual characters in the male bird. He showed their strict dependence upon an endocrine secretion, since castration brings their immediate regression, and gave a simple but accurate algebraic expression of this regression. He also deduced from the effects of total castration of females that the ovary normally secretes a substance that inhibits the evolution of plumage and the development of spurs. This was the first demonstration of the inhibitory action of an endocrine secretion.

In his pioneer study on the experimental production of sexual inversion and hermaphroditism Pezard defined the conditions required for the grafting of testicular translants. With this procedure he showed that a minimal, or threshold, amount of the specific hormone must be secreted in order to elicit a given secondary sexual character, each character responding to a different threshold amount. Thus Pezard introduced into endocrinology the “all or none” law, classical in other domains of physiology. In 1922 Pezard began the most active years of his scientific life, working closely with Fernand Caridroit and with Knud Sand of Copenhagen. Their papers, treating the experimental production of gynandromorphic hens, demonstrate the important implication of their results for genetics. They concluded that hormones obviously do not interfere with the fundamental genotypic complex, but act as regulators of dominances. These hormones operate, as in sex, not as creating agents but as exteriorization factors. They neither destroy existing genes nor provide new genes.

Pezard’s work, which exerted a marked influence on biologists, found artistic expression in his creation of strange and beautiful birds, such as hens decorated with a cock’s brilliant feathers and proud comb. His reputation was great outside France, which failed to give him a university professorship and left him to teach high school pupils.

BIBLIOGRAPHY

Pezard’s writings include “Sur la détermination des caracteres sexuels secondaires chez les Gallinacés,” in Comptes rendus hebdomadaires des seances de l’Academie des sciences,153 (1911), 1027-1030; “Sur la determination des caracteres sexuels secondaires chez les Gallinaces, greffe de testicule et castration post-puberale,” ibid.,154 (1912), 1183-1186 ; “Developpement experimental desergots et croissance de la crete chez les femelles des Gallinaces,” ibid.,158 (1914), 513-516; “Transformation experimentale des caracteres sexuels secondaires chez les femelles des Gallinaces,” ibid., 160 (1915), 260-263; “Loi numerique de la regression des organes erectiles consecutive a la castration post-puberale,” ibid., 164 (1917), 234-236; Le conditionnement physiologique des caracteres sexuels secondaires chez les Oiseaux (Paris 1918); Edition du Bulletin Biologique de la France et de la Belgique; “Facteur modificateur de la croissance normale et loi de compensation,” in Comptes rendus hebdomadaires des séances de l’Academie des sciences,169 (1919), 997-1000; “Castration alimentaire chez les Coqs soumis au regime carne exclusif,” ibid., 1177-1180; “Secondary Sexual Characteristics and Endocrinology,” in Endocrinology,4 (1920), 527-541; “Castration intrapubeale et generalisation de la loi parabolique de regression,” in Comptes rendus hebdomadaires des seances de l’Academie des sciences,171 (1920), 1081-1084; “Loi du ’tout ou rien’ ou de constance fonctionelle du testicule considéré comme glande a secretion interne,” ibid.,172 (1921), 89-91; and “Temps de latence dans les experiences de transplantion testiculaire et loi du ’tout ou rien,’ ibid., 176-179.

See also “Numerical Law of Regression of Certain Secondary Sex Characters,” in Journal of General Physiology,9 (1921), 271-283; “Notion de ’seuil differentiel’ et explication humorale du gynandromorphisme des Oiseaux bipartis,” in Comptes rendus hebdomadaires des seances de l’Academie des sciences,174 (1922), 1573-1576; “Notion de seuil differentiel et masculinisation progressive de certaines femelles d’oiseaux,” ibid.,175 (1922), 236-239; “Interpenetration testiculaire chez les Coqs castres incompletement,” ibid ., 284-287, written with Caridroit; “L’heredite sex-linked chez les Gallinaces. Interpretation fondee sur l’existence de la forme neutre et sur les proprietes de l’hormone ovarienne,” ibid., 910-913, written with Caridroit; “L’action de I’hormone testiculaire sur la valence relative des facteurs allélo morphes chez les Ovins,” ibid., 1099-1102, written with Caridroit; “La loi du ’tout ou rien.’ Expose general,” in Journal de physiologic et de pathologie generale,20 (1922), 200-211; “La loi du ’tout ou rien’ et le gynandromorphisme endocrinien,” ibid., 495-508; “Caracteres sexuels secondaires et tissus interstitiels,” in Comptes rendus de la Societe de biologie,88 (1923), 245-248; “Critique de la theorie de Bouin et Ancel,” ibid., 333-336; “Feminisation d’un Coq adulte Leghorn dore,” ibid.,89 (1923), 947-950, written with Sand and Caridroit; “Le gynandromorphisme biparti experimental,” ibid., 1103-1106, written with Sand and Caridroit; and “Gynandromorphisme biparti fragmentaire d’origine mâle,” ibid., 1271-1274, written with Sand and Caridroit.

See also “Productions experimentales du gynandromorphisme biparti chez les Oiseaux,” in Comptes rendus hebadomadaires des seances de l’Academie des sciences,176 (1923), 615-618, written with Cariodroit; “Modifications raciales papr greffe ovarienne chez les Coqs,” in Comptes rendus de la Societe de biologie40 (1924), 737-740, written with Sand and Cardroit,"Poecilandrie d’origine endocrinienne chez les Gallinaces,” ibid.,90 (1924), 676-679, written with Sand and Caridroit,"Potentialities homologues et potentialites heterologues chez la poule domestique,” ibid., 677-680; “Remarques au sujet de l’heredite sex-lin ked chez les Galliances,” ibid., 935-938, written with Caridroit; “Survive d’unm tranplant testiuculaire adtif enpresence d’un transplnat testculaire actif enpresence d’un ovaire producteur d’oeufs murs chez la Poule domestique,” ibid., 1459-1462,:Evolution et fonction d’un tranplant ovarienchez un coq adulte Leghorn dore,” ibid.,91 (1924), 1075-1078, written with sand and Caridroit; and “Lle gynandromorphisme en mosaique et les dysharmonies encdocriniennes chez les Gallinaces,” ibid., 1116-1119, written with Sand and Caridroit.

See also “Modifications hormono-sexuelles chez les Gallianaces adultes et theorie de la forme specifique,” in Comptes rendus hebdomadaires des seances de l’Academie des sciences178 (1924), 2011-2014, written with Sand and Carioidroit,"Lle gynandromorphihsme biparti experimental. Recurrences raciales dictees par la mue automnale et caracteres transitoirese de certaines modifications pigmentaries “ibid.,177 (1924), 1087-1090, written with Sand and Caridroit; “Le gynandromorphhisme experimental et le non antagonisme des glandes sexuelles chez les Gallinaces adultes,"in Comptes rendus de la Societe de biologie92 (1925), 427-430, written with Sand and .

Cardroit ,;L’evoolution des potentialites chez la Poulette,” ibid., 495-498; “Une notion nouvelle’l’existence d’un seuil differential racial dans certains complexes hybrides des Gallianacfe,"ibid., 566-569, written with Sand and Caridroit; “Inversion sexuelle du plumage observes chez nos sujets lors de la recen te et notion duy seuil hormolnique,” ibid.,93 (1925), 1094-1096, written with Sand and Caridroit,"Quelques faits nouveaux concernant les greffes d’ovaires effectuees sur le Coq domestique,"ibid.,94 (1926), 520-523, written with Sand and Caridroit; “Analyse de quekques deviations sexuelles secondaires chez lkes Gallinacess,” ibid.,741-744, written with Caridroit; “La bipartition longitudinale de la plume faits nouveaus concernant le gynandromorphisme elementaire,” ibid., 1074-1078, written with Cariodrooit; and La presence de l’hormone testiculaire dans le sang d’un Coq normal. Demonstration directe fondee sur la greffe autoplastique de cretillons,” ibid.,95 (1926), 296-300, written with Caridroit.

See further “Les hormones sexuelles et le gynandromorphisme chez les Gallinaces,” in Archives de biologie, 36 (1927), 541–647, written with Sand and Caridroit; “Les caractères sexuels secondaires,” in Masson’s Traité de physiologie, XI (Paris, 1927), 125–163; “Inversion sexuéllé autonome d’une Cane de Rouen,” in Comptes rendus de la Societe de biologie, 96 (1927), 1295–1298, written with Caridroit; “Classement des seuils differentiels du plumage chez la poule domestique,” ibid., 1372–1375, written with Caridroit; “Remarques concernant la loi du ’tout ou rien,” ibid.,97 (1927), 442–446; “État actuel de la theorie de l’interstitielle,” ibid., 620–623; “Die Bestimmung des Geschlechtsfunktion bei den Huhnern,” in Ergebnisse der Physiologie, 27 (1928), 552–656; and La determination de la fonction sexuelle chez les Gallinaces, Masson, ed. (Paris, 1930).

A. M. Monnier