254 



Anatomif and Physioloc/y of the 



closed ; but at the time of parturition it is widely dilated, thus 

 iorming a free and open passag^e from the vagina to the interior 

 of the uterus. The coats of the uterus are three, and are united 

 to each other bj areolar tissue : the external or serous coat is 

 smooth and continuous with the lining membrane of the abdo- 

 men ; it gives support to the viscus, and by its reflections forms the 

 two broad ligaments. The middle or muscular coat varies con- 

 siderably in strength and thickness, referable to impregnation or 

 non-impregnation ; it is thin and comparatively weak in the latter 

 case, and its fibres, which interlace each other in every direction, 

 become greatly increased during gestation. On the muscular coat 

 the expulsion of the foetus from the uterus in delivery partly 

 depends. The internal or mucous coat has a velvety appearance, 

 and it secretes the menstrual fluid ; but its princijml use in the 

 lower animals is to form a bond of connexion between the mother 

 and her young ones, by which their vitality is preserved and their 

 development effected. To this w'e shall hereafter more especially 

 refer. 



a.—The bouv of the uterus. 

 ;,._Tlie OS uteri, 

 c, c. — The horns, one of which is laid open. 

 r/,'rf._The Fallopian tubes, with their fimbriated 



extremities, 

 e, c— The ovaries. 



/,/. — Tlie broad lij^aments. 

 (J. — The uriiiary bladder. 

 h. — The opening; of the bladder. 

 i — The vagina cut open to show the passage 

 leading to the bladder and os uteri. 



We will now add a few remarks on the causes of cestrum, im- 

 pregnation, and the development of the foetus. The terjn oestrum 



