. Cunningham's Text-book of anatomy. Anatomy. THE FORMATION. OF THE EMBEYO. 37 cavity of the primitive mid-brain is converted into the aqueductus cerebri, which connects the third with the fourth ventricle. After the anterior and posterior neuropores (p. 31) are closed, the cavity of the neural tube is, for a time, a completely enclosed space. Subsequently the mesoderm, which in the meantime has surrounded the tube, becomes differentiated, in its immediate neighbourhood, into three membranes. The innermost of the three is closely connected with the walls of the neural tube and is called the pi
. Cunningham's Text-book of anatomy. Anatomy. THE FORMATION. OF THE EMBEYO. 37 cavity of the primitive mid-brain is converted into the aqueductus cerebri, which connects the third with the fourth ventricle. After the anterior and posterior neuropores (p. 31) are closed, the cavity of the neural tube is, for a time, a completely enclosed space. Subsequently the mesoderm, which in the meantime has surrounded the tube, becomes differentiated, in its immediate neighbourhood, into three membranes. The innermost of the three is closely connected with the walls of the neural tube and is called the pia mater. The outermost, known as the dura mater, is dense and resistant, and the intermediate membrane is a thin lamella called the arachnoid. As the membranes are formed, spaces are differentiated between them. The space between the dura mater and the arachnoid is the subdural space, and that between the arachnoid and the pia mater is the subarachnoid space. After a time a median perforation, the median aperture of the fourth ventricle ( foramen of Magendie), and two lateral perforations pierce the dorsal wall of the fourth ventricle and the pia mater which covers it, and thus the fourth ventricle becomes connected with the subarachnoid space. It is stated also that a perforation passes through the medial wall and the covering pia mater of a portion of each lateral ventricle which is called its inferior horn, throwing those portions of the lateral ventricles also into communication with the subarachnoid space. THE FORMATION OF THE EMBRYO. Neural plate Ectoderm of amnion Mesoderm of amnion Primitive streak Body stalk. llantoic diverticulum from entoderm vesicle Cephalic end of embryonic area Pericardial mesoderm'" Mesoderm entoderm vesicle Entoderm Xotochord Fig. 48.—Schema of Sagittal Section of Embryonic Area and Amnion before the Folding of the Area has commenced. Amnion cavity Neural tube - Region of anterior neuropore Ectoderm of amnion The transformation o
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectanatomy, bookyear1914
