jg OBSTETRICAL PHYSIOLOGY. 



Rouget, who has established the fact that the utero-Qvarian artery, on 

 arriving at the body of the uterus, near the Fallopian tube, divides into 

 curved or spiral bouquets of vessels which open into veins, like the heli- 

 cine arteries of the male cavernous sinus. Along the inferior border of 

 the ovary, this artery forms a series of branches that wind and twist 

 exactly like the arterial ramifications at the root of the corpus cavernosum^ 

 penetrating the stroma of the ovary, and giving rise to spirial convolu- 

 tions. The venous system composes the uterine sinuses — contorted 

 venous canals not unfrequently spiral, like the arteries. 



The uterus is, therefore, an erectile organ like the penis, and its erection 

 is connected with the periodic haemorrhage from its inner surface. The 

 venous sinuses in the meshes of the muscular tissue, crossing each other at 

 the hilus of the ovary, are partially compressed, and the immediate result is 

 the distending and erection of the bulb of the ovary. This modification in 

 the ovarian circwlation extends to the uterus, so that both are in a state 

 analogous to erection ; the prolonged tension is communicated to the ves- 

 sels and capillaries of the mucous membrane ; the epithelium is shed, leav- 

 ing the tunic of the capillaries exposed, and this soon gives way, whence 

 results the haemorrhage, which persists as long as the erection and obstruc- 

 tion to the free flow of blood through the veins continues. This is the 

 case in the human female, but it must be admitted that, in several animals, 

 the erectile formations are either in a rudimentary condition or entirely 

 absent. 



In the Bitch the bulb of the ovary is moderately developed ; but the 

 arteries of the uterus, although contorted in a spiral form, are not such a 

 vascular mass of vessels as to constitute a real erectile organ. In Rumi- 

 nants, small vascular masses or formations are observed near the cotyle- 

 dons, which may be taken to represent the spongy texture of the human 

 uterus. 



With regard to the season at which this " heat " takes place, it has been 

 observed that it is usually the spring-time, when food becomes plentiful, 

 especially with herbivorous animals. The Carnivora are in heat during 

 winter. The Mare is usually in heat from April to June, or later. With 

 the Cow whose calf is sold at from one to two months old, with a view to 

 utilizing the milk, the season of course is varied : as care is taken to in- 

 duce conception again as soon as the lacteal secretion begins to diminish ; 

 but it has been observed that midsummer is more particularly the rutting 

 period. And the " heat " in Sheep, though naturally present in Septem- 

 ber, is usually only shown during summer, because the Ewes are kept apart 

 from the Ram at the natural time, in order that the lambs may be born at 

 a favorable season — the spring ; and the period of suckling over (four or 

 five weeks), they may be weaned when the herbage is tender and nutritious. 

 And in other circumstances, particularly with animals bred for the butcher, 

 the rut is induced sooner by putting the Ewes in contact with the Ram at 

 an earlier period, so as to obtain two or three lambings in the year. 



The Bitch is in heat from December to February, or in the autumn and 

 spring-time. 



The Cat is in this state in January and February, and also in the spring 

 and autumn ; sometimes the heat appears three or four times a year, and 

 the animal may produce young as frequently, though in the wild state it 

 seldom does so more than twice a year. 



The Pig manifests rutting in October or November ; at least that is the 

 period when it is usually put to the male ; and it may be put a second 



