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supposed to be possessed of the early stages in the developement of 

 that ovum, consists chiefly of inferences from observations made on 

 the ovum of the bird. 



But there exists a period in the history of the ovum of the mam- 

 mal, regarding which we have hitherto scarcely any direct or posi- 

 tive knowledge. It appeared, therefore, highly desirable to obtain 

 a series of observations in continuous succession on the earliest stages 

 of developement. In conducting this investigation, the author pur- 

 posely confined his attention to a single species, namely, the rabbit, 

 of which he examined more than a hundred individual animals. 

 Besides ova met with in the ovary, apparently impregnated, and 

 destined to be discharged from that organ, he has seen upwards of 

 three hundred ova in the Fallopian tube and uterus ; very few of the 

 latter exceeding half a line in their diameter. The results of these 

 investigations have compelled the author to express his dissent from 

 some of the leading doctrines of embryology, which at present prevail, 

 as respects not only the class Mammalia, but the animal kingdom at 

 large. The following are the principal facts which the author has 

 observed in the developement of the mammiferous ovum. 



The difference between the mature and immature ovum consists 

 in the condition of the yelk ; the yelk of the mature ovum contain- 

 ing no oil-like globules. Both maceration and incipient absorption 

 produce changes in the unimpregnated ovum, which in some respects 

 resemble those referable to impregnation. During the rut, the num- 

 ber of Graafian vesicles appearing to become prepared for dischar- 

 ging their ova, exceeds the number of those which actually discharge 

 them. Ova of the rabbit which are destined to be developed, are in 

 most instances discharged from the ovary in the course of nine or ten 

 hours post coitum ; and they are all discharged about the same time. 



There is no condition of the ovum uniform in all respects which 

 can be pointed out as the particular state in which it is discharged 

 from the ovary ; but its condition is in several respects very different 

 from that of the mature ovum ante coitum. Among the changes 

 occurring in the ovum before it leaves the ovary, are the follow- 

 ing : viz. the germinal spot, previously on the inner surface, passes 

 to the centre of the germinal vesicle ; the germinal vesicle, previously 

 at the surface, returns to the centre of the yelk ; and the membrane 

 investing the yelk, previously extremely thin, suddenly thickens. 

 Such changes render it highly probable that the ovary is the usual 

 seat of impregnation. The author considers this view as being not 

 incompatible with the doctrine that contact between the seminal 

 fluid and the ovum is essential to impregnation, since he has found, 

 in the course of his researches, that spermatozoa penetrate as far as 

 to the surface of the ovary. The retinacula and tunica granulosa are 

 the parts acted upon by the vis a tergo, which expels the ovum from 

 the ovary. These parts are discharged with the ovum, render its 

 escape gradual, probably facilitate its passage into the Fallopian tube, 

 and appear to be the bearers of fluid for the immediate imbibition of 

 the ovum. After the discharge of the ovum from the ovary, the 

 ovisac is obtainable free from the vascular covering, which, together 



