Talk:Paper - The development of the hypophysio-portal system in man (1933)

THE DEVELOPMENT OF THE HYPOPHYSIO- PORTAL SYSTEM IN MAN

By PAUL G. ’ESPINASSE, M.A. (Oxon.)

Lecturer in Zoology, University College, Hull

In recent papers Popa and Fielding (1,2) have described in the human subject a system of vessels running in the stalk of the pituitary which they call the hypophysio-portal veins. The development of this system is the subject of this paper. MATERIAL AND METHOD

I have had the advantage of being able to study two early embryos, one of 11-9 mm. and the other not measured but probably about 5 weeks from con- ception, placed at my disposal at Oxford by Prof. Goodrich, for whose kindness in allowing me to examine and photograph them I am most grateful. I have also made use of three later specimens of about 2, 4, and 5 months, generously given to me by medical practitioners. These pituitaries were sectioned at 10 p together with all the surrounding structures after fixation in mercury formol soon after death. The sections were stained with Mallory’s connective tissue stain, modified for certain sections to show particular points. The series were then examined, the courses of the chief vessels determined, and the most important sections were photographed.

OBSERVATIONS

Plate I, fig. 1, shows a transverse section of an 11-9mm. embryo at the region in which the carotid arteries are bent to conform with the flexure of the embryo. The arteries therefore lie in the plane of the section. The mesoderm immediately surrounding the brain, richly supplied with blood vessels, is about to form the meninges. Vessels are carried into the substance of the brain by this tissue growing in. When, later on, the different membranes can be distinguished, the vessels can be seen to be accompanied into the brain by pia mater and by arachnoid tissue. Each vessel comes in this way to be surrounded by a small

diverticulum of the sub-arachnoid space—the space of Virchow-Robin. According to the observations of Hughson (3.4) upon the adult dog and cat and the embryo pig, the pituitary complex in these forms lies wholly within the dura mater which covers the floor of the sella and is reflected to form the diaphragma sellae. The cord of cells from the buccal epithelium marking the ‘closed tube of the original buccal invagination (Rathke’s pocket) breaks down before the completion of the meninges, so that this total enclosure of the complex is developmentally comprehensible. The arachnoid membrane also encloses the complete organ. There is inside this and separated from it by a part of the sub-arachnoid space, a layer of pia mater. Hughson demonstrated