PLACENTA (FUNCTIONS). 



that flows around it, becomes thinner, and 

 finally gives way by extension. But long be- 

 fore this stage arrives, the whole of this por- 

 tion is shut out from the maternal circulation, 

 and the subsequent metamorphoses are di- 

 rected to the strengthening of the more limited 

 space which remains. It is on this account 

 that the strong border of decidua is formed 

 around the margin of the now restricted area. 

 The base of the placenta now consists of the 

 tough and resisting chorion ; while that por- 

 tion alone of the decidua which is strength- 

 ened externally by the uterine walls is retained 

 to form the opposite boundary. Ultimately, 

 as the current of maternal blood flows with 

 increasing force into the placenta in propor- 

 tion to the growth of the latter, this becomes 

 subdivided by the decidual septa, which ap- 

 portion the entire organ into separate placen- 

 tulae, and thus the larger supplies necessary 

 to the increasing exigencies of the foetus are 

 disposed of without danger of rupture to any 

 portion of the organ. 



The changes in the more minute structures 

 which belong to the foetus are not less inter- 

 esting. The profuse development of fine 

 capillaries within the fcetal tufts, which is so 

 conspicuous from the third to the sixth month, 

 is connected not only with the functions of 

 respiration and nutrition of the foetus, but also 

 with the growth of the villi themselves. But 

 when the period of viability of the foetus has 

 arrived, the proportionate amount of capillary 

 vessels within the villi becomes greatly re- 

 duced, until finally only the original stems of 

 the vessels are left. And this relative reduc- 

 tion of the channels through which the foetal 

 blood flows, becomes more marked, until, as 

 the time of birth approaches, many of the villi 

 become more or less obliterated, and cease to 

 admit blood, often in consequence of that calca- 

 reous degeneration which, from the frequency 

 of its occurrence, may be regarded rather as 

 a normal process significant of natural decay 

 than as an evidence of any morbid or preter- 

 natural change. 



The series of metamorphoses is closed by 

 the degeneration of the materials which bind 

 the placenta, and consequently the foetus, to 

 the uterus. The layer of decidua forming the 

 connecting medium between the uterus and 

 the foetal structures, in common with the rest 

 of this membrane, suffers slow disintegration, 

 and its component cells are converted into 

 molecular fat. And now the strength of the 

 adhesion being gradually diminished, it only 

 remains for the contractile power of the ute- 

 rus to be evoked in order to accomplish the 

 separation together of the foetus and placenta, 

 like ripe fruit detached from the parent bough. 



The illustrations of this article marked, " ad na- 

 turam," are from original drawings and preparations 

 in the possession of the author. For the rest of the 

 figures the authorities are given. 



The usual signs are employed : for an inch " ; 

 for a line "'; and for the amplification x. 



The following tabulated arrangement of the prin- 

 cipal contents will facilitate reference to the several 



723 



subjects, as well as to the books quoted in the foot 

 notes of this article. 



UTEKUS AND ITS APPENDAGES. 



OVARY. 



Normal anatomy. 

 form, 547. 



dimensions and weight, 547. 

 position and connections, 548. 

 Component parts : 



1. protecting parts or tunics, 548. 



peritoneum, tunica albuginea, 548. 



2. parenchyma or stroma, 549. 



3. Graafian vesicles, 550. 



4. blood-vessels and nerves, 552. 

 Functions of the Ovary. 



the developmental changes in the ovicapsules, and 

 the process of emission of ova, 552. 



1st stage, origin of the ovicapsules, 554. 



2nd stage, growth, maturation, and prepara- 

 tion for dehiscence, 555. 



3rd stage, rupture or dehiscence, and escape of 

 ova, 558. 



4th stage, decline and obliteration of the ovi- 

 capsules, 561. 



A. without impregnation, 561. 



B. after impregnation, 563. 

 spontaneity of the emission of ova, 566. 

 nature of the corpus luteum, 564. 569. 

 classified arrangement of all the conditions which 



the Graanan follicle exhibits during evolution 

 and involution, 570. 



summary of the conclusions which these conditions 

 afford with reference to questions in obstetric 

 and forensic medicine, 571. 

 Development and Involution of the Ovary. 



the origin of the ovary, and the alterations which 



it undergoes at different periods of life, 571. 

 Abnormal Anatomy of the Ovary. 



effects of extirpating the ovary, 573. 

 deficiency and arrest of development, 573. 

 atrophy and hypertrophy, 573. 

 displacement, hernia, 573. 

 diseases of the tunics, 

 inflammation, 574. 

 ulceration, rupture, 574. 

 hypertrophy, calcification, 574. 

 diseases of the proper tissues, 

 hyperaemia, 576. 

 inflammation, 576. 

 suppuration, 577. 

 simple, multiple, multilocular, and proliferous 



cysts, 578. 



the contents of ovarian cysts, 582. 

 fluid contents of cysts, 582. 

 quantity and rate of effusion, 582. 

 composition of the fluids contained in ovarian 



cysts, 583. 

 hydatids, 584. 



solid contents of ovarian cysts ; sebaceous and 

 sudoriparous glands ; fat; hair; teeth; true 

 bone, 584. 



origin of the solid contents of cysts, 586. 

 foetus contained in the ovary (?); the question 



of ovarian gestation considered, 586. 

 examples of supposed ovarian gestation, 587. 

 solid enlargements of the ovary, 591. 



cartilaginous and ossific formations, 591. 

 cancer, colloid or alveolar ; medullary and 



scirrhous, 591. 

 scrofulous tubercles, 593. 



THE PAROVARIUM. 



Structure and development, 593. 

 Abnormal states, 597. 



THE FALLOPIAN TUBE OR OVIDUCT. 



Normal Anatomy. 



form ; dimensions, 597. 

 situation and connections, 598. 

 separate parts and divisions, 599. 

 internal orifice, 599. 

 uterine portion of the tube, 600. 

 canal, 600. 

 external orifice, 600. 

 pavilion or infundibulum, 601. 

 fimbriae, 601. 



tubo-ovarian ligament, 602. 

 structure of the coats or tunics, 603. 

 blood-vessels and nerves, 604. 

 Functions of the Fallopian Tube. 



reception and transmission of ova and spermatic 



fluid, 605. 



first steps in the process of impregnation, 608. 

 the changes which the ovum undergoes in the tube, 



609. 

 Development of the Fallopian Tube. 



formation of the oviduct out of the duct of MUller, 



613. 



SA 2 



