82 Translation from Purkinje 



TRANSLATOR'S NOTES 



(i) This is a cordial and generous reference to von Baer's Epistola^ announcing the discov- 

 ery of the mammalian ovum. It included a complete confirmation and extension of Purkinje's 

 observations" (see translator's note 5). Anyone who has studied the various types of yolk 

 granules in the bird's egg can readily understand how natural it was for von Baer in 1827 to 

 homologize the "granules" of the mammalian "cumulus oophorus" with the white yolk 

 granules of Purkinje's "cumulus" (see Sarton^"). Von Baer saw the germinal vesicle in young 

 mammalian follicles but failed to see it in his "ovulum." He concluded that the entire 

 Graafian "vesicle" is homologous with the oocyte of the hen and that the "ovulum" is the 

 transformed germinal vesicle. 



In 1833 Coste" reported at a session of the Paris Academie des Sciences that he had identified 

 the germinal vesicle in the rabbit's egg and this was noted a month later in Froriep's Notizen. 

 Purkinje refeired to these observations in his 1834 article^^ "Ei." Since his own efforts to find 

 the germinal vesicle in mammals had been in vain, like Coste's earlier ones, he was not pre- 

 pared to accept the finding at the time. In the following year, however, Valentin and Bern- 

 hardt in Purkinje's laboratory confirmed Coste and this was published in Bernhardt's thesis"" 

 (1834). In the 1834 memoire,^^ Coste reported the disappearance of the germinal vesicle before 

 ovulation in the rabbit, although in the previous year he thought he had recognized it in an 

 oviducal egg. Purkinje's suggestion that the disappearance of the germinal vesicle at the 

 time of ovulation be investigated did not bear fruit for fifty years. At the time the whole situa- 

 tion was fraught with insuperable difficulties, and Purkinje's fear that "this naturally difficult 

 matter might be an unapproachable mystery" was justified (see Meyer,^" chap. VIII). Von 

 Baer thought he had seen the germinal vesicle, as such, extruded from the ripe frog's egg. 

 He was probably observing polar body formation. After his convincing evidence that the 

 germinal vesicle is no longer present just before ovulation in hen and frog he would have 

 been confused indeed if he had known that it was still intact in the tubal eggs of the dog. This 

 is one of the few vertebrates in which the first maturation division does not begin until after 

 ovulation (Van der Stricht,^^' ^^ Evans and Cole'^). The understanding of maturation had to 

 wait upon the discovery and interpretation of mitosis and on the unraveling of the histo- 

 genesis of the spermatozoon and they in turn depended on the development of staining 

 methods. 



(2) See Bartelmez," p. 328. 



(3) Purkinje does not say here which of the "lines" he means. There were some eight "lines" 

 in use in various European countries at the time, all in the neighborhood of 2.2 mm. In his 

 article "Ei"^" (1834) he gives a series of measurements of hens' oocytes in "Vienna" lines and 

 his collaborator Valentin"^ in 1835 employed the same unit. The Vienna line corresponds to 

 2.195 mm. It ^vould be interesting to know whether the line developed from Aristotle's 

 smallest unit of measurement, a millet seed. A hundred of the dry seeds which I ha^e 

 measured averaged 2.85 mm. in length and 1.82 mm. in width. 



(4) Purkinje mentions this term casually as if it were familiar to his readers. When he in- 

 troduces a ne^v name he is careful to call attention to the fact, so it must be assumed that 

 tliis one had been used before. I have, however, failed to find it anywhere except in the two 

 editions of the present work. Valentin in his textbook^" (18351 implies that the observation 

 of "a clear agranular and perfectly transparent spot at the center of the cicatricula had been 

 made by Fabricius ab Aquapendente, Harvey, and others and had been readily repeated by 

 many naturalists." There is nothing in Fabricius, or Harvey, or any eighteenth-century author 

 I have read, to indicate that the "poms" had been seen in the hen's egg. There are several 

 figures in the literature before 1825 which show what can readily be interpreted as the 

 germinal vesicle of other eggs. The best of these are Poll's figures in his sumptuous work'*" on 

 "testaceous" molluscs (1791; see pi. 16, fig. 18, showing a group of young oocytes from the 



