INTERNAL ORGANS OF GENERA TION. 49 



ence than centre, is the nucleus — the gsrminal vesicle, ox vesicle of Purkifige, 

 a most important portion of the ovum ; it has the appearance of a very 

 small clear ring, measuring about i-6oth of a line in diameter, and upon 

 its surface is a dark spot, the macula germinativa. This is always observed 

 as a simple rounded body, measuring from i-2ooth to i-3ooth of a line in 

 diameter ; it is rarely found double or as an aggregate of granules, except 

 in miniature ova. 



The large flexuous arteries supplying the ovary, are from the utero- 

 ovarian trunk; they spread over the spaces in the tunica albuginea, 

 before entering the hilus of the organ to be distributed in its interior. 

 The veins are extremely large, and form a very close plexus around the 

 gland {bulb of the ovary), emptying themselves into the vena cava near 

 the renal veins. The lymphatics pass to the sub-lumbar ganglia, and the 

 nerves come from the small mesenteric plexus. 



Differences. 



Cow, Sheep, and Goat. 



In the Cow the ovaries are relatively smaller than in the Mare, but 

 their form and structure are the same. Each is lodged in a depression 

 or sacculus of the broad ligament which is more or less deep, and the 

 Graafian vesicles are visible through the tunica albuginea. The same 

 arrangement is observable in the Sheep and Goat. 



Pig- 

 In the Pig the ovaries are comparatively large, oblong bodies, with an 

 irregular tuberculated or lobulated aspect, due to the Graafian vesicles, 

 which, when well developed, project beyond the surface of the organ, 

 instead of remaining within it. When these ovisacs enlarge, the stroma is 

 scanty in proportion. Each ovary is enclosed within a peritoneal sac, near 

 the opening of which it has a pedunculate attachment. The posterior 

 wall of this sac, as we have seen, appears to be formed by the wdde and 

 deep pavilion of the Fallopian tube. 



Bitch and Cat. 



There is nothing particular to indicate in the ovaria of the Bitch and 

 Cat, except that the ligaments suspending them to the spine are very 

 short, and they are contained in a fold of peritoneum. 



Development. 



The development of the ovaria and the ova is very interesting. In the 

 Mare the ovaria of the foetus are, compared wdth the uterus, of an 

 immense size, and at six months are almost as large as in the adult. In 

 aged animals they become atrophied, and it is not unusual in old Mares 

 to find either one or both in an unhealthy condition. Not unfrequently they 

 are hypertrophied, and their fibrous envelope and stroma are much thick- 

 enened. Sometimes the vesicles are greatly enlarged, and converted into 

 cysts which contain either a limpid, sanguinolent, or purulent fluid, secreted 

 from their walls. Flandrin cities the case of a Mare, one of whose ovaries 

 weighed 26)^ pounds, andmeasured 145^ inches in its long, and 12 inches 



4 



