44 



OVUM. 



The first modern discovery, which intro- 

 duced a far greater accuracy into the study of 

 ovology than existed previously, was unques- 

 tionably that of the germinal vesicle in the 

 ovarian ovum of birds, by Purkinje, of Bres- 

 lau, in 1825 *, an observation which led di- 

 rectly to the ascertainment of the general fact 

 that such a vesicle exists invariably in the 

 ovarian ovum of all animals. The extension 

 of this discovery to a variety of oviparous 

 animals, we may consider as due, in the first 

 instance, to Von Baer and R. Wagner. 



The next important discovery in chronolo- 

 gical order, which contributed, in an eminent 

 degree, to remove one of the greatest difficul- 

 ties in our subject, was that made^by Von 

 Baer, in 1827, of the minute ovum of mam- 

 malia, or true viviparous animals, f The dis- 

 covery of the nature of the mammiferous 

 ovum was rendered complete in 1834, by the 

 observation of the germinal vesicle first by 

 Coste and somewhat later but independently 

 by T. Wharton Jones ; and the knowledge 

 of the mammiferous ovum was greatly ex- 

 tended and confirmed by the observations of 

 G. Valentin and Bernardt, of Breslau. 



Malpighi, Wolff, Dollinger, Von Baer and Pander 

 took a prominent part, but only that which belongs 

 to the structure of the ovum itself. 



* This discovery was first announced in a small 

 work, entitled Symbolae ad Ovi Historiam ante Incu- 

 bationem, Auct. Joann. Evang. Purkinje ; printed at 

 Leipzig in 1825, on the occasion of the celebration of 

 Blumenbach's Semisecular Jubilee. A second edi- 

 tion in 4to, with two lithog. plates, appeared in 1830. 

 Purkinje is also the author of the Article Ei in the 

 Berliner Encyclopsedisches Worterbuch, in 1834. 



f See the Epistola de Ovi Mammalium et Hominis 

 Genesi, Auct. Car. Ern. De Baer, published in 4to., 

 at Leipzig, in 1827; and the interesting Com- 

 mentary on or Supplement to the same in'Heusinger's 

 Journal; and the translation of both of these 

 writings in Breschet's Re'pertoire d' Anatomic et de 

 Physiologie. 4to. Paris, 1829. As I shall have 

 occasion to "return to the history of this dis- 

 covery, I will not enter on farther details here ; but 

 it is right to state that Messrs. Prevost and Dumas 

 may in some measure be considered to have shared 

 in the merit of the discovery ; as, in an extended and 

 highly illustrative series of experiments, instituted 

 by them as early as 1824, the}' were led to the 

 conclusion that the ovules of mammiferous animals, 

 of extremely minute size, were really contained in 

 the Graafian follicles previous to conception ; and 

 they even appear to have twice seen in the contents 

 of very advanced follicles, a small spherical body 

 which could be no other than the ovule. See An- 

 nal. des Scien. Nat., torn, iii., 1824, p. 135. But Von 

 Baer first demonstrated this body with precision, 

 and explained its relations to the follicle, &c. 



J Coste's discovery of the germinal vesicle in the 

 rabbit, was communicated to the public in the 

 Comptes rendus for 1833 ; it is fully described in 

 his Kecherches sur la Ge'ne'ration des Mammiferes, 

 &c. ; 4to. Paris, 1834. In 1835, Thomas Wharton 

 Jones read a paper to the Royal Society of London, 

 containing an account of his observations on this 

 vesicle in the mammiferous ovum, made without a 

 knowledge of those of Coste in the autumn of 1834 ; 

 but this paper was not printed in the Transactions 

 of that year. It was afterwards published in the 

 Lond. Med. Gazette, in 1838, p. 680. This dis- 

 covery was confirmed and extended by Valentin 

 and Bernardt, whose observations are recorded by 

 the latter in his work, Symb. ad Ovi Mammal. Hist, 

 ante Praegnationem, Vratislavias, 1834. 

 See G.Valentin's Handbuch der Entwickelungs- 



The nature of the germinal vesicle itself 

 next attracted the attention of ovologists, 

 and a farther addition to the knowledge of its 

 structure was made by Rudolph Wagner, of 

 Gottingen, in 1835, by the discovery in it of a 

 minute particle or mass of fine granules, to 

 which he gave the name of macula germi- 

 nativa, or germinal spot.* The subsequent 

 researches which that author instituted on 

 the earliest condition of the ovula in the whole 

 series of animals, contributed,' more than any 

 others of the same r period, to establish the 

 doctrine of a general uniformity in the struc- 

 ture and mode of origin of the ova of animals.f 

 Although it appeared, from the researches of 

 R. Wagner, and has been made still more 

 apparent from late observations, that in 

 several classes of animals the germinal macula 

 loses its determinate form and is subdivided 

 and diffused, as it were, in the germinal vesicle, 

 yet the more circumscribed form of this body, 

 in its earliest condition, and its general preva- 

 lence, as a constituent part of the vesicle 

 in almost all animals, seem to indicate the 

 analogy of that vesicle with the true nucleated 

 cell of other parts of the animal body. 



After the general nature and structure of 

 the ovum had been ascertained by the several 

 discoveries now mentioned, numerous and 

 important researches followed one another 

 in rapid succession, giving greater extent, 

 minuteness, and accuracy to, and in some 

 instances modifying and correcting, the know- 

 ledge previously acquired. Among the authors 

 of these researches, besides those already 

 mentioned, the names of Rathke, J. Miiller, 

 Prevost and Dumas, Barry, Reichertj Bi- 

 schoff, Kolliker, and Vogt, occupy the most 

 prominent place. Of these, and others, more 

 special mention will be made in the progress 

 of our history of the ovum and its develop- 

 ment. But, as my present object is to place 

 before the reader only the principal disco- 

 veries which may be regarded as the ground- 

 work of the scientific knowledge of our 

 subject, I will only farther call attention at 

 this place, to the influence which the ob- 



geschichte des Menschen, &c. ; 8vo. Berlin, 1835, 

 at p. 14. The part of this work relating to the 

 structure and formation of the ovum, was translated 

 and published by Dr. M. Barry, in the Edin. Med. 

 and Surg. Journal, No. 127, 



* The observations of R. Wagner on this subject, 

 were made towards the end of 1834. This discovery 

 was first published in the 1st Edit, of his Lehrbuch 

 der Vergleich. Anat. 8vo., Leipzig, 1834 35, pp. 

 320 and 352, and in Muller's Archiv. for the latter 

 year, p. 373. 



f His more extended researches are described 

 in the work entitled, Prodromus Historic Genera- 

 tionis Hominis atque Animalium ; folio, Leipzig, 

 1836. With two copper-plates and very numerous 

 figures. These and the researches of Valentin, are, 

 with reference to the ovum, peculiarly interesting 

 and important as the immediate precursors of the 

 Microscopic Researches of Schwann. See also, the 

 Beitrage zur Geschichte der Zeugung und Entwic- 

 kelung, by R. Wagner ; published in the Trans, of 

 the Roy. Bavar. Acad. of Sciences, 4to., Munich, 

 1837. 



R. Wagner is also the author of the Article Et 

 in Ersch and Gruber's Encyclopaedic. 



