DEPARTMENT OF EMBRYOLOGY. 101 



Extending his studies to the lymphatics of the stomach, Mr. Cash 

 found, by injecting the retroperitoneal sac in embryo pigs, that 

 numerous lymphatic sprouts pass into the stomach at the esophageal 

 opening around which they develop, growing out in all directions. 

 Two large vessels sweep ventralward under the spleen to the greater 

 curvature and toward both cardia and pylorus, anastomosing with 

 other branches from the ring. In embryos 60 to 70 mm. long the 

 stomach is well covered with lymphatics and several vessels are sent 

 from the retroperitoneal sac directly to the pylorus, through the 

 duodenal mesentery. In older specimens the plexus in the pyloric 

 region is much more dense and its vessels smaller than in other parts 

 of the stomach. Two large lymphatic vessels can be seen micro- 

 scopically, one in the loose, subserous tissue, the other in the sub- 

 mucosa. These are very dense and are connected by a less dense plexus 

 which traverses the muscularis. Numerous branches from the sub- 

 mucosal plexus run in close relation to the blood-vessels. 



A detailed morphological study of the development of the seminal 

 vesicles in the human embryo has been made by Dr. Ernest M. Watson. 

 He traces their structure and topography from the time they first 

 appear as lateral evaginations from the Wolffian ducts in fetuses 80 

 mm. long up to birth. Dr. Watson has also completed an accurate 

 study of the verumontanum in the human embryo, tracing its 

 development and noting particularly the morphogenesis of its glandular 

 elements. He finds that definite glandular tubules, arising from the 

 evagination of the urethral mucosa, appear at the fourteenth week 

 (fetuses about 100 mm. CR length). A second group of tubules of 

 prostatic origin appear in fetuses 130 mm. CR length. Finally, in 

 fetuses 221 mm. CR length a third group of tubules is observed in 

 the mucosa of the prostatic utricle. All three groups can be clearly 

 identified in the 270 mm. fetus. 



WTiile studying the fissura hippocampi in human embryos, Dr. 

 Marion Hines has discovered that, although the transitory fissures, 

 which are usually seen on the median wall of the cerebral hemisphere 

 in the brains of embryos of 14 to 20 weeks' development, are artefacts, 

 in embryos from 7 to 14 weeks the waU is not perfectly smooth. It 

 shows at this time a shallow but complete infolding from the rostral 

 to the caudal pole. The nervous tissue which lies at the bottom of 

 this groove consists of an inner, narrow, nucleated zone, and a mde 

 area devoid of cells. In the early stages this is the only part of the 

 cerebral hemisphere in which the matrix and marginal velum of His 

 are distinct. In an 11-mm. embryo it occupies the medio-dorsal 

 sector of the cerebral invagination; at 14 mm. it lies more medial, and 

 at 20 mm. it is almost centromedial. This sulcus, deepened by 

 maceration, is doubtless the fissura hippocampi of amphibians and 

 reptiles. Ventral to the fissura, in the rostral medial sector, is an 



