DR. MARTIN BARRY'S RESEARCHES IN EMBRYOLOGY. 323 



70. The granules forming this tunic being soluble in water (9.), the fluid of a large 

 Graafian vesicle, or some thin albumen, is a preferable medium in which to view this 

 structure, as well as all the other parts connected with the ovum. 



71. In a future paper I sliall show that the tunica granulosa accompanies the ovum 

 into the Fallopian tube. 



The Memhrana granulosa. 



72. Von Baer-|~ gave this name to a stratum of granules lining the internal sur- 

 face of the Graafian vesicle. That author's description of the membrana granulosa 

 appears to be very accurate so far as it goes; but there remains something to be said 

 respecting it, for to this day doubts are en-tertained whether this stratum of granules 

 really constitutes a membrane, though Dr. Pockels recently demonstrated it to be 

 such in a mature Graafian vesicle of the Deer J. Von Baer has also figured it§, but 

 so little magnified that no adequate idea is thus given of this membrane. 



73. It is composed of the peculiar granules of the ovisac (Plate VIII. fig. 71.)- 

 With the proper membrane of the ovisac, now the lining membrane of the Graafian 

 vesicle, the membrana granulosa is in contact onlyH, appearing very easily to break 

 down and separate from it. The membrana granulosa may be made to escape by 

 rupturing a Graafian vesicle under the compressor ; when, after the escape of the 

 other contents, it slowly passes out in a membranous form^. It is then possible to 

 roll portions of this membrane on themselves, and even to obtain folds, as seen in 



Plate VIII. fig. 71. 



74. The granules forming the internal surface of this membrane are sometimes 

 found less densely aggregated together than those in other parts ; portions of the 

 membrane projecting like villi into the fluid of the Graafian vesicle. This mem- 

 brane is also frequently found to be of very unequal thickness, projecting at some 

 parts much farther into the cavity of the Graafian vesicle than at others. The cause 

 of these apparent villosities and projections will be presently explained, when the 

 manner of origin also of this membrane will be shown {7^^- 



which I am now describing as the spherical tunica granulosa. He probably saw it in no other state than that 

 to which I have just referred, viz. flattened or removed by pressure against the membrane of the ovisac. 



t Lettre, &c., p. 18, and Commentaire, p. 47. 



X MiJLLEE's Archiv, 1836, Heft ii. S. 193—204. Tab. vi. 



§ Lettre, &c., fig. xi. 



II It was observed by Baer, that between the membrana granulosa and the internal surface of the Graafian 

 vesicle there was no "liaison organique." Commentaire, p. 41. 



By maceration, as observed by Baer also, the membranous structure of this granulous lining may be well 

 seen in situ from the exterior of a Graafian vesicle ; the membrana granulosa separating as a distinct vesicle, 

 and a space intervening between it and the walls of the cavity it lines. 



% It is often more yellow in its colour than the other granulous contents of the Graafian vesicle. 



2 t2 



