300 
Dr Duckworth , The histology of the 
It appears then that the adherent part of the wall of a 
blastocyst is retained in the sections, and even the low power 
drawings (Figs. 1 and 2) reveal the presence of villous processes. 
Higher magnification shews that mesoderm has not yet reached 
the great majority of these villi, and the inference is to the effect 
that the stage is an extremely early one, possibly as early as the 
middle of the first week of development. 
In specimens of this kind particular attention is directed to 
the following features, and these are dealt with briefly in the 
sequel. 
(1) The implantation of the blastocyst in the uterine wall*. 
(2) The changes in the uterine wall determined by the 
arrival of the blastocyst f. 
(3) The history and changes of the embryonic tissues sub- 
sequent to the attachment of the blastocyst : with special 
reference to : 
(a)j The mode of communication whereby the maternal 
* Tlie mode of implantation of the blastocyst is well known to vary in the 
several Orders of Mammalia. The literature upon this subject is extenswe, but 
has been admirably reviewed by Mr Assheton, Phil. Trans. Roy. Soc. London, 
Series B, Yol. 198, pp. 143 — 220, “The morphology of the Ungulate Placenta,” 
1906, and by Dr A. Robinson in the Hunterian Lectures, 1903 (published in the 
Journal of Anatomy and Physiology , Vol. xxxvin.). 
Selenka (op. cit. supra ) has demonstrated the mode of attachment which obtains 
in animals of the genera Semnopithecus and Hylobates among the higher Primates. 
Peters (“Uber die Einbettung des menschlichen Eies &c.” Deuticke, Leipzig, 
1899), has clearly described the appearances and surroundings of an early human 
ovum, and demonstrated the apparent resemblance of the processes herein to those 
shewn by Graf. v. Spee (full references in Hertwig’s Handbucli der vergleichenden 
und Experimentellen Entwickelungsgeschiclite der Thiere, Band n. p. 366, and also 
p. 342) to obtain in the Guinea-pig. 
Other classical accounts are reviewed and criticised by Strahl in Hertwig’s 
Handbuch (p. 342). 
Siegenbeek van Heukelom’s research will be particularly mentioned in the 
sequel. The original account is in the Archiv fur Anatomie und Physiologie, 
Anatomischer Theil, 1898. 
Frassi has quite recently published a description of the appearances of a human 
embryo (in utero) of the age of ten days : Archiv fur Mikroskopische Anatomie und 
Entwicklungsgeschichte, 1907, Band 70, Drittes Heft. 
f In monkeys of the family Cercopithecidae, the decidua capsularis is not found. 
The uterine surface is described by Selenka (“ Placentaranlage &c.” p. 7) as raised 
into a wall or circumvallation around the blastocyst. The uterine tissues become 
oedematous. The uterine glands are represented (Studien Taf. ii. Fig. a) as some- 
what dilated at their mouths. “Cell-nests” derived from uterine epithelial cell- 
elements are believed by Selenka to become transformed into “ syncytia ” which in 
turn embrace the ends of the embryonic villous processes. Reference should also 
be made to Strahl in Hertwig’s Handbuch, Band ii. pp. 326 et seq. For the 
comparative study in different mammalian Orders, Strahl’s work must be consulted, 
and also the memoirs of Assheton and of Robinson (op. cit.). 
X In this connexion, reference is necessary to the literature dealing with the 
formation and the nature of the walls of the intervillous spaces. Again Strahl’s 
memoirs and his contribution to Hertwig’s Handbuch, Vol. ii. must be mentioned. 
Voigt (for references v. infra) has also lately published a valuable paper on this 
subject. 
