TEE FCETUS. l«lt 



2. The foetus being isolated, the chorion is studied with rofjard to shape and exteraal 

 aspect. To seo the relations of its internal face with the otiier annexes, we may lesorttoa 

 plan which gives good results with the foetus of Ruminants. This consists lu tilling tlie 

 allantois and amnion by small openings with different-coloured fluids. The limits of the two 

 sacs can then be very well made out tlmmgh the chorion, while their reciprocal relations can 

 also be observed. With Solipeiis, the allaiitoid cavity must uecessariiy be opened; tiie mem- 

 brane of that name is partially separated from the inner surface of the chorion by blowing ia 

 air along the principal divisions of tlie vessels of the cord, by means of a straw or blow-tube. 



3. 'I'o complete the study of the amnion and the allantois of Ruminants, it is best to blow 

 in air beneath the chorion, utter removing tlie contents. The chorion ia then carefully taken 

 away, in breaking through — by means of the fingers and forceps— the laminal tissue uniting 

 these two membranes; in the same way are destroyed the fasciculi which bind the allantoia 

 to tlie amnion. In Solipeds, nothing is more easy than to inflate tiie amnion, and to study 

 its shape and relations. The cliorial layer of the allantois is demonstrated as already de- 

 scribed ; a similar procedure is employed to show the existence of the amniotic layer, which ia 

 more easily done tban with the other. 



4. The vessels of the umbilical cord and placenta should be injected, and to make an 

 injection penetrate satisfactorily, tlie placental vessels, with the foetus and chorion, should be 

 placed in tepid water for some time. 



The annexes of the fatus comprise : 1. A membranous envelope exactly 



DIAGRAM OF THE FCETAL MEMBRANES OF A HAICHAL. 



pc, Zona pellucida with villi, and sz, the remainder of the extra-embryonal somatoplcure con- 

 stituting the chorion; arn, amnion; AC, cavity of amnion ; uv, umbilical vesicle; at, allantois; 

 ALC. cavity of the allantois; e, ectoderm, or outer layer of the embryo (epiblast); M, mesoblast 

 (or middle layer); H, endoderm of the embiyo (alimentary canal). 



moulded on the uterus, and known as the chorion. 2. A second ovoid sac in- 

 cluded in the first, and containing: the foetus — the amnion. 3. The aUantois — a 

 membrane formed of two layera spread over the inner surface of the chorion 

 and the e.\ternal face of the amnion, as well as coverino^ the parts between these 

 two envelopes. 4. A small pyriform bladder con<?titutin^ the umhiliml vesicle. 

 5. The placenta — a collection of vascular tufts which graft the young creature 

 to the mother. 6. The umbilical cord, composed of vessels that attach the foetus 



