THE ^CETUS. 903 



pedicle ; their surface is convex, and perforated by numerous openings, into which the 

 placental tufts pass. They have always a yellowish colour which, added to their 

 external characteristics, gives them the appearance of a moril mushroom. 



With regard to the placentse, they repeat, on the surface of the chorion, the disposition 

 of the cotyledons on the uterus. They are vascular, concave patches, closely embracing 

 the cotyledons, and showing on their surface a multitude of long ramifying p:ipilla3, 

 which bury themselves in the cotyledonal cavities. They are attached to the chorion by 

 a very thick, short, vascular pedicle". 



In the Sheej) and Goat the arrangement is the same, except that the cotyledons are 

 hollowed out in their centre, like a cup, and into this cavity the placenta is inserted. 



Chorion. — This membrane corresponds to the inner face of the uterus, in the inter- 

 placental points ; its internal surface is united by lamellar connective tissue to tlie 

 amnion and allantois. Its general form is a repetition of that of the uterine cavity. 



AUantois. — Very different trom that of the Mare, and otherwise much less com- 

 plicated, the allantois of Euminants is a very elongated cavity, whose middle portion 

 receives the insertion of the urachus, and whose extremities are prolonged into the two 

 oomua of the chorion. This sac, which is an expansion of the urachus, is idways 

 reversed on one of the sides of the amnion. At times the hippomanes is found floating 

 in the liquid it contains. 



Amman. — Altogether like that of Solipeds, this membrane is readily resolved into 

 two lamina, and presents on its inner surface a great number of little, yellowish-white, 

 epidermic patches, more especially visible on the amniotic covering of the cord. 



- Umbilical cord. — This comprises two arteries and two veins ; the latter forming one 

 trunk on their entering the abdomen. To reiich the chorion, these vessels only traverse 

 the amniotic cavity. They are accompanied by the urachus, which at their extremity 

 presents the dilatation that results in the allantoid sac. 



Umbilical vesicle. — This pouch disappears at nn early period, and not a vestige of it 

 is to be found after the formation of the abdominal parietes. 



2. Pig. — The placenta is formed by an expansion of the villous tubercles, as in 

 Solipeds. 



The chorion has not a body and two cornua, but is merely an elongated sac, whose 

 two extremities are in relation with the adjacent foetuses. The inner face corresponds, 

 as in Euminants, with the amnion and allantois. The latter is the same as in the Cow, 

 though it is very much shorter. 



The umbilical vesicle, amnion, and cord are also the same as in Ruminants. 



3. Caknivoka.— The placenta is a thick cincture, surrounding the middle portion of 

 the chorion. The latter resembles that of the Pig. 



The allantois is disposed, in principle, as in Solipeds. 



The umbilical vesicle, which remains very developed at all periods of fcetal lite, 

 resembles in shape the allantois of the Pig ; being a transversely elongated sac included 

 between the amnion and the inner allantoid lamina, and provided at its middle portion 

 with a narrow pedicle, which is prolonged into the umbilical cord; its walls are 



extremely vascular. „ , ., - , . ,^ ^i i, i ■ 



The amnion is lined, internally, by the mner lamma of the allantois. 



The umbilical cord has, as in Solipeds, an allantoid portion ; but it is extremely 

 short, and enveloped in a wide fold of the allantois. 



Eesults The comparative examination of the disposition of the placenta may 



furnish valuable indications as to the procedure to be adopted in practising artificial 

 delivery • as the surgical manojuvres should necessarily vary with the extent and disposi- 

 tion of the points of union existing between the uterus and the foetal envelopes. 



With this practical object in view, we believe that it is useful to divide the 

 domesticated animals into two groups: those which have a eimjjZe and those which 

 have a multiple placenta. The first group may be subdivided, according as the simple 

 placenta is general or local. . ,, „ „ . , , , 



This division is summed up in the following table : 



„ , I Mare, 



f Simple Placenta I ^^f*"^™^ \ Sow. 



Animals 



, Multiple Placenta 



Local and Circular . | q . 

 I Cow. 



Goat. 



