Contribiitioiis to the Knowledge of the Developement of the 



Fætal Membranes in Odontoceti. 



Plates VI and VII. 



L 



Ln the preceding literary survey, the most important works in which the subject of the fætal membranes in Cetacea was 

 treated, have been mentioned. I will now shortly refer to these. 



Eschricht (39) in 1837, describes the surfaces of the chorion as very much wrinkled, and covered with villi V2 

 line distant from one another, and states that the villi had a stalk, and that the free end expanded in the form of a globe, 

 like the head of a cauliHower. In the depressions between the rugæ, there were small villi. A beautiful capillary net-work 

 was noticed in the crowns of the villi. They correspond to the depressions in the mucous membrane of the uterus, which 

 is very vascular. Eschricht also describes numerous ramified uterine glands, and believes that their secretion is taken up 

 through the veins into the villi. — Owen (Anat. of Vertebrates, vol. Ill, p. 732) remarks that the foetal membranes 

 extend into both the horns of the uterus. After having mentioned the villosity of the chorion, the uterine mucous membrane, 

 and the smooth poles of the chorion, he compares the diffused placenta to a broad "placenta zonata". 



It is,, however, as already stated, to Sir William Turner's (43) famous work that we owe most thanks for the 

 fact that the Cetacean's placenta is no longer so unfamiliar a subject as it was a generation ago. In his examination of tiie 

 "Blue Rorqual" (Balænoptera Sibbaldii, Gray) stranded at Longniddry in 1869, Turner describes the folds and wrinkles 

 of the chorion, the villous character of its surface, and the presence of a well-defined spot which is without villi. In 1871 

 appeared his important treatise on the uterus and the foetal membranes in Orca gladiator, Lacépéde. He there gives 

 an account of the structure of the uterus, the fætal membranes, the position of the fætus, and makes a general comparison 

 between the formation of the placenta in Cetacea, and the diffuse placenta of other Mammals (Mare, Sow). The uterine 

 mucous membrane is divided into a cryptal layer and a glandular layer, of which the former is the more highly vascularised. 

 The chorion is diffusely beset with villi, but presents 3 bare spots, viz. 2 small ones, one at each pole, and 1 larger one 

 corresponding to the os uteri internum; the patches that are bare of villi correspond to the uterine cavity's natural 

 openings. — The scattered villi of the chorion are distinctly visible to the naked eye, but their form and arrangement, on 

 being slightly magnified, present many variations, as they stand now in parallel rows, now in little groups, and again more 

 dispersed, composed as a rule of several smaller, secondary villi. As regards their histological structure. Turner found tliat 

 the villi consisted of a fine connective tissue, in which were imbedded numerous round and spindle-shaped bodies; but on 

 the other hand, he found no epithelial covering, supposing, very rightly, that the epithelium cells had fallen off during treatment. 

 The chorion consisted of 2 layers, an outer layer with villi, and an inner thin, transparent layer, between which the vessels 

 were divided. The capillary net-work of tiie villi passed uninterruptedly into these subchorionic vessels, which then became 

 the roots of the umbilical veins. The intravillous capillary plexus lay, in relation to the capillary system, in the walls of 

 the uterine crypts, while the subchorionic layer was situated beneath the plane formed by the surface of the general uterine 

 nmcous membrane. The umbilical cord consisted of 2 arteries and 2 veins and the urachus. The amnion formed a continuous 

 bag from one horn of the chorion to the other, but did not extend quite to the poles, though farthest in the left horn which 

 contained the fcetus. Its surface was beset with small yellowish brown bodies. 



That portion of the amnion at the back of the fætus was attached to the inside of the chorion by a very tine 

 fibrous tissue, but at the attachment of the allantois to the chorion, i. e. that part corresponding to the ventral surface of the 

 foetus, the amnion passed on the outside of the cylindrical horn of the allantois, and was accompanied by this membrane to the 



