206 EXTRACTS AND ABSTRACTS FROM FOREIGN JOURNALS. 



water, the envelope quickly breaks, and the primitive molecules are 

 seen accumulated around the central vesicle. Plate 7, fig. 10. 



On the 30th day, the thick fluid is perceived of a yellow colour, and 

 few globules ; and on the 40th day after the infecting coitus very few 

 globules, and those for the most part ruptured, are found in the white 

 and thinnish fluid. 



(To be continued at p. 225 .) 



anfc 3flbstract from ^foreign 



[From Mullers Archives, 1842.] 



Meyer on the Existence of a Distinct Membrane surrounding the Yelk 

 in the Ova of Mammalia. Repeated observations made principally on 

 the ova of the pig, have satisfied Dr. H. Meyer of the existence of a 

 peculiar yelk membrane. He found this fact to be most clearly 

 demonstrated in ova taken from ovaries which had been a few hours in 

 alcohol. 



The appearances upon which the existence of this membrane is pre- 

 sumed are as follows : 



1 . The yelk granules are not in immediate contact with the inner 

 surface of the chorion, but cease with a regular border, at a greater or 

 less distance from it. 2. The interspace thus formed is filled with a 

 yellowish granular matter. 



Several experiments have proved, that this matter is a distinct mem- 

 brane. 



1. In one instance, on the bursting of an ovum, the yelk granules 

 passed through the rent in the chorion, not scattered or separated, but 

 in a mass, which was distinctly seen to be kept together by an envelope, 

 by which it was attached to the edges of the rent, forming a sort of 

 hernia ; and within the almost empty chorion, a plicated, pale-coloured 

 granular looking membrane was distinguishable. 



2. Although the presence of the interspace between the yelk and the 

 chorion does not prove that the former is enclosed in a peculiar mem- 

 brane, yet it does prove that it is surrounded by something more than 

 the chorion. That this additional envelope, however, is really a mem- 

 brane, is proved, partly by the above observations, and partly by the 

 result of an easy experiment. 



3. If a drop of a solution of caustic potass be brought in contact 

 with an ovum under the microscope, the chorion is very easily dissolved, 

 yet the yelk remains unaltered ; and it can now be readily proved, that 

 the yelk granules still retain an envelope, by moving the glass covering 

 the object, backwards or forwards, or by causing it to make pressure 

 upon it, and increasing the pressure until the covering is ruptured 

 and the yelk granules escape, the envelope remaining in the form of a 

 granular, but otherwise structural membrane. 



Dr. Meyer remarked, as had previously been done by Wagner, that 



