722 UTEROGESTATIOX. 



animals, -n-itli the exception of tiie Simiac, in -v-\-hich the structure probably agrees 

 closely Avith the human, the elements of uterine structure are very clearly present, 

 and the uterine blood-vessels may be recog-nised as such, not being dilated into vide 

 sinuses or lacv\na3, but retaining more or less the capillary form of distribution : al- 

 though in some instances the capillaries have undergone considerable dilatation, and 

 geem to be passing into the condition of venous sinuses. (For a very instructive 

 view of the structure of the placenta in these various animals and their bearing 

 upon the nature of the i^lacental structure in general, the reader is referred to 

 Professor Turners Lectures on the Structure of the Diffused, the Polycotyledonous 

 and the Zonary forms of Placenta, as published in the Journal of Anatom}- and 

 Physiology, vol. x.. p. 127. Oct. 1875, and separately, 1870. There may also be 

 consulted Yon Baer's Entwickelungsgeschichte. 1839. and Eschricht, De oi-ganis 

 qua3 Respirationi et Xutritioni Foetus Mammalium inserviunt, Hafnia3, 1837.) 



Bclni'wn of the I'frrlnr Glands to tlic Pliiciiital titriictiirc. — It has long been 

 known that in the placentation of various mammals the uterine glands undergo 

 an increased development, and it has been supposed that they enter into structural 

 and functional relation with the fcetal villi ; but more precise knowledge is still 

 wanting as to whether, and to what extent this relation is of the nature of an 

 actual penetration of the cavities of developed and dilated glands hj the cho- 

 rionic villi. It was shoAAii by Dr. Sharpey (Miiller's Physiology by Baly, vol. ii. 

 p. 1574) that thedecidua which enters into the fonnation of the zonular placenta 

 of the dog. and doubtless of other camivora, consists of a hypertrophical part of 

 the uterine mucous memlu-ane of corresponding figure, in which the main ducts 

 of the largely developed glands become dilated at their orifices into utricular 

 saccules or pouches, that hollow membranous processes containing foetal vessels 

 rise from the chorion, from among the smaller vascular villi, and apply their 

 flattened summits to the widened mouths of the gland ducts, and enter a short 

 way within the saccules : while these receptacles are filled with a whitish semi- 

 fluid secretion and are lined with an epithelium, which also covers the intriided 

 part of the fcetal process. As pregnancy advances, the chorional and decidual 

 structures are further interlocked, and the arrangement becomes more intricate. 

 Decidual, that is, maternal blood-vessels are abundantly distributed round the 

 villi of the chorion, which they closely cover. These vessels are larger than ordi- 

 nary capillaries ; they are unsupported by decidual stroma, and are separated 

 along M-ith the rest of the placenta in parturition. 



The observations of Shaipey appeared to receive confirmation from the inves- 

 tigations of E. H, Weber (Zusatze zur Lehre vom Baue, kc, der Geschlechts- 

 organe, 184G,) and Bischoff (Entmck, des Hundeeies, 184.5,), and by many these 

 observations have been held to prove satisfactorily a connection between the 

 glands and placental formation. But Dr. Sharpey has expressed himself cautiously 

 on this general question, and more recent observations tend rather to throw 

 doubts on the penetration of the uterine glands by the villi of the chorion. 



More especially the observations of Ercolani (Mem. of the Acad, of Bologna, 

 1868 and 1870) and of Turner (loc. cit.) seem to show that it is possible that the 

 saccules described by Sharpey may be formed in the uterine decidua of the car- 

 nivora independently of the glands ; and they are disposed to think that these 

 saccules are produced rather in the interglandular tissue. From an examination 

 of the whole evidence on this point and an investigation of the structure and 

 formation of the placenta in different animals, contained in the lectiu-es prcAdously 

 quoted. Turner has ascertained that in the diffused fonn of placenta the uterine 

 glands open in the sow into feebly vascular intervals between the vascular crypts 

 in which the foetal chorionic fringes are sunk, and not into these crypts them- 

 selves ; that in the mare the glands open on elevated ridges between the vascular 

 crypts which receive the foetal villi, and only in the Cetacea (Orca gladiator) 

 did he find gland apertures in some of the placental crj-pts. Again, the maternal 

 cotyledons of the i-uminants are destitute of utricular glands, and these are 

 confined to the sunk intercotyledonous part of the uterine membrane. In the 

 zonal placenta of the camivora, as previously stated. Turner failed to trace the 

 uterine glands into the recesses of the decidua which receive the prolongations of 

 the chorionic plates and villi, constituting the foetal portion of the placenta ; and 



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