EARLIEST CHANGES IN THE OVUM. 03 



Barry's opinion, the germinal vesicle does really cease to exist (as indeed, 

 observers before Barry had generally supposed), very soon after coition.* 

 But, at the same time, he thinks that it does not always disappear before 

 the ovum leaves the ovary. f In many cases it cannot be discerned in the 

 ovarian ovum several hours after the coitus ; and mostly, not when the 

 ovum has entered the Fallopian tube. But, in other cases, it is often dis- 

 coverable many hours after coitus, both in the ovarian ovum and even in 

 ova which have passed into the Fallopian tube. It is, however, invariably 

 dissolved before the commencement of the other metamorphoses of the yolk, 

 presently to be described.^ 



It is worthy of remark, that in those intestinal worms of which the ova 

 are very transparent, Kolliker distinctly observed, that there was a period 

 during which the germinal vesicle was no longer to be seen, although the 

 development of cells, preparatory to the formation of the embryo, had 

 not yet commenced. And, in these instances it appeared to him, that the 

 germinal spot disappeared before the germinal vesicle. 



Professor Wagner, || on the other hand, seems to agree with Dr. Barry 

 in respect of the fate of the germinal vesicle. For he says that, although, 

 owing to the difficulty of the subject of investigation, he has not arrived at 

 any absolutely conclusive result, yet he regards it as a certain fact, that 

 within the germinal vesicle the germinal spot gives rise to new generations 

 of cells which grow with great rapidity, and eventually cause the solution or 

 destruction of the parent-cell, or germinal vesicle. He states, that he has 

 distinctly witnessed this process of cell-formation by the germinal spot in 

 the ova both of frogs and Mammalia. 



The observations of M. Vogt on Alytes Obstetricans,H are rather in 

 favour of the view entertained by Barry and Wagner. For he states, that 

 when the ova of this batrachian approach maturity, the germinal spots 

 increase in number, and that when the vesicle is burst by pressure, they 

 escape in the form of transparent vesicles, which, in ova mature enough to 

 leave the ovary, often amount to as many as forty. Moreover, he observed, 

 that in ova which had been discharged from the female and fecundated 

 only a few hours, the germinal vesicle, which before was visible even to 

 the naked eye, could now by no means be discerned, and that the germinal 

 spot also seemed to have disappeared, though, on farther search, several 



* Entwickl. der Saugeth. und des Menschen, p. 42. f Ibid. 



$ The germinal spot, however, Bischoff supposed, from what he observed in the rabbit, 

 not to be dissolved, like the germinal vesicle, but to be set free, and subsequently to undergo 

 peculiar changes to which reference will again be made. Recently, however, Bischoff has 

 had reason to doubt the correctness of the above view, for in two cases he could not detect 

 any spot in the perfectly isolated germinal vesicle of bitches' ova. (Entwick. des Hunde-eies, 

 p. 42.) $ Muller'sArchiv. 1843. p. 77. 



|| Lehrbuch der Physiologic, Second edit. p. o3. 



Ti Untersuchungen uber die Entwick elung der Geburtshelfer-Krb'te. Solothurn. 1841. 

 p. 4. 



