The aim of Tredern' s dissertation was to tell the 

 preliminary story of the avian egg and its hatching. He 

 submitted his dissertation for open public discussion by 

 scientists on April 4, 1803. 9 The introduction contained an 

 important statement specifying the extensive material to 

 which the author had referred, presented in several divisions. 

 These divisions are: 



I. NATURAL HISTORY OF THE EGG. Color, form, size, weight, 

 and taste of the egg, properties of the shell, the behavior of 

 birds during incubation and its duration, the number of eggs, 

 and so on. 



II. ABNORMALITIES OF EGGS (deviations from normal 

 structure) . Information was included about eggs becoming 

 luminous in the dark, about eggs turning into glass and 

 amber, and even about cocks laying eggs. The last case, 

 obviously, deal with hens displaying feathers like those of 

 cocks, or having voices like those of cocks, features which 

 are not rare, but which promote superstition. 



III. CHEMISTRY OF EGGS. This division included investiga- 

 tions about the effect of different reagents and physical 

 agents (temperature and humidity) on individual constituents 

 of the egg. 



IV. INCUBATION OF THE EGG. Tredern wrote that he had 

 carefully investigated eggs from the first hours of incubation, 

 from the appearance of a recognizable embryo to the hatching 

 of the chick, partly with the naked eye, partly with the aid 

 of a lens, accompanied by descriptive, life-size drawings. In 

 this section he reported changes in the egg membranes, including 

 the amnion and chorion, during the whole period of incubation, 

 the changes in the yolk and the egg white, and also in the 

 amniotic fluid and the blood- carrying vessels (obviously those 



Tredern, DISSERTATIO INAUGURALIS MEDICA SISTENS OVI 

 AVIUM HISTORIAE ET INCUBATIONIS PRODROMUM, QUAM 

 PRO GRADU DOCTORIS SUMMISQUE IN MEDICINA ET 

 CHIRURGIA HONORIBUS, PRIVILEGIIS AC IMMUNITATIBUS 

 RITE CAPESSENDIS, A.D. IV Aprilis MDCCCVIII publico 

 eruditorum examini subjecit Ludovicus Sebast. Comes ab 

 Tredern, Estonia — Rossus, Jena. 



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