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PROGRESS OF MICROSCOPICAL SCIENCE. 
own opinions on the subject, lie has given those of the most recent 
foreign authorities, and thus has given the reader a useful summary of 
the work done on this subject. We hope, when the blocks have been 
received, to lay the paper fully before our readers. 
The precise period at which the Laminar Membrane appears . — 
Dr. Joulin, who has been known for his researches on the placenta 
some years since, presented to the Academy of Medicine a memoir 
in which he endeavoured to show that the chorion at term did not, 
as is generally described, cover the foetal surface of the placenta, 
but that it was replaced by a membrane of new formation called the 
“ laminar membrane.” The object of his present communication is to 
show the precise period at which the chorion disappears, when new 
membrane takes its place. The conclusion he arrives at is that the 
chorion begins to disappear from the foetal surface of the placenta 
about the tenth or eleventh week of utero-gestation, the new membrane 
being formed at first in connection with the great vessels, and gradu- 
ally extending over the entire placenta. Microscopically it consists 
of fibres in distinct layers, and can be readily distinguished from 
the other membranes surrounding the foetus. 
The Structure of the Uterus has been very fairly investigated by 
Dr. Snow Beck, and his researches will be found more fully stated in 
the ‘ Obstetrical Transactions ’ (vol. xiii.). In his paper he advances 
views somewhat different from those generally taught. He does not 
admit the existence of a separate mucous membrane lining the uterus. 
He describes the walls of the uterus as consisting of two parts: — 
(a) The contractile tissue destined to expel anything contained in the 
uterine cavities, and which exists in greatest amount at the outer and 
middle portions, whilst towards the inner surface it is divided into 
smaller striae with considerable spaces between them, (b) The soft 
tissue which lines the internal surface, where it exists alone to some 
thickness, and afterwards penetrates a considerable distance into the 
substance, lying between the striae and bands of the contractile tissue. 
It is destined to form the placenta which is thrown off at the com- 
pletion of parturition, together with the inner layer from the whole of 
the inner surface of the uterus, as decidua. But it is only the inner 
layer of the soft tissue which comes away, the principal portion yet 
remaining in the inner portion of the walls. The decidua and the 
formation of the placenta appear to be the natural development of the 
soft tissue which exists at the inner surface of the unimpregnated 
uterus, and at the completion of parturition it is thrown off from the 
surface as now useless products, and there does not appear any suffi- 
cient reason to apply special designations to particular portions of it. 
