Royal Society. 209 



" On the Ova of Women and Mammiferous Animals, as they exist 

 in the Ovaries before Impregnation." By Thomas Wharton Jones, 

 Esq. Communicated by Robert Lee, M.D., F.R.S. 



After reviewing the accounts given by various authors of the struc- 

 ture of the ovaries, corpora lutea, and ova in different tribes of ani- 

 mals, the author proceeds to the anatomical description of the ovaries 

 in the human species, which he finds to correspond with those of the 

 Mammalia generally, and to consist of a parenchyma or stroma, and 

 an envelope or indusium, derived from the peritoneum. The stroma 

 immediately under the peritoneal envelope is condensed into the form 

 of a tunic, to which the peritoneum closely adheres, and which has 

 received the name of the tunica albuginea, or indusium proprium. The 

 vesicles of De Graaf are imbedded in this tunic, and are situated prin- 

 cipally near the surface of the ovary : in the human species they are 

 about one fifth of an inch in diameter. The proper capsule of the 

 Graafian vesicle is composed of two layers -, the outer being thin, 

 dense, and vascular; the inner, thicker, softer, and more opake. 

 The nucleus of the vesicle consists of, 1st, a granular membrane 

 inclosing : 2ndly, a coagulable granular fluid j 3rdly, a circular mass 

 or disc of granular matter, termed by Baer the proligerous disc, con- 

 nected with the granular membrane on the prominent side of the 

 vesicle, and presenting in its centre, on the side towards the interior 

 of the vesicle, a small rounded prominence, called the cumulus, and 

 on the opposite side a small cup-like cavity, hollowed out of the cu- 

 mulus j and, 4thly, the ovum, which is contained in the cavity just 

 mentioned. The human ovum is so small as to be only just percep- 

 tible to the naked eye, being the 150th part of an inch in diameter. 

 It has a soft transparent envelope of considerable thickness, and 

 contains a substance composed of grains, adhering together by the 

 intervention of a delicate mucous tissue. At the inner surface of the 

 envelope, the author discovered a delicate transparent vesicle, about 

 the 900th part of an inch in diameter, and having on one side a small 

 elevation, which, projecting among the grains composing the walls of 

 the granular sac, fixes the vesicle in its place. The author considers 

 this vesicle as being analogous to that described by Professor Pur- 

 kinje in the cicatricula of the immature eggs of birds, and which exists 

 also in the ova of other oviparous animals, and is termed by Baer the 

 germinal vesicle. 



The author has also examined the ova of the cow, sheep, sow, rab- 

 bit, rat, and mouse, and has found in all these animals a germinal 

 vesicle, differing in no essential particular from the human structure, 

 and in size bearing a proportion to that of the ovum as one to six. 



Although there is, at first sight, a considerable resemblance be- 

 tween the nucleus of the vesicle of De Graaf and the immature yelk 

 of the egg of a bird, the author thinks, contrary to the opinion of 

 Baer, that there is no real analogy between them -, because, in the 

 Graafian vesicle of the Mammalia there is no membrane surrounding 

 its nucleus similar to the vitellary membrane of the ovum in birds, 

 nor does this latter membrane appear first under the form of a gra- 

 nular membrane. The vesicle of Purkinje consists merely of a delicate 



Third Series Vol. 7. No. 39. Sept. 1835. 2 E 



