DEPARTMENT OF EMBRYOLOGY. 85 



In the course of the preceding investigation, Dr. Lee obtained a specimen 

 which was so injected as to reveal the distribution of the lymphatic vessels in 

 the wall of the aorta. In view of our meager knowledge concerning the 

 lymphatic drainage of arterial walls, this successful specimen has proved 

 worthy of careful study. Dr. Lee finds that there is an extensive lymphatic 

 plexus at the junction of the media and adventitia and that it anastomoses 

 with a more superficial plexus of larger lymphatic vessels. 



Abdominal Chromaffin Body. 



From the observations of earlier investigators, we are famihar with the 

 size, shape, number, color, and distribution of the abdominal chromaffin 

 bodies in the dog, cat, rabbit, and man, but regarding the function of these 

 apparently important structures and their relation to the medullary substance 

 of the adrenal glands, which they so closely resemble, we know very little. 

 With the purpose of obtaining more definite information on this subject, 

 Doctors Wislocki and Crowe have carried on a series of experiments in which 

 varying proportions of the adrenal glands were removed and graded radium 

 emanations applied to the parts of the gland that were left in position. The 

 resultant changes in the abdominal chromaffin body were then observed. In 

 dogs in which the adrenals had been destroyed it was found that the abdominal 

 chromaffin body at the time of death of the animal showed every evidence of 

 normal or slightly increased activity, and the investigators deemed it probable 

 that it is capable of performing the secretory function normally subserved by 

 the medulla of the adrenal. On the other hand, there is conclusive proof 

 that the cortex of the adrenal is necessary to Hfe. 



In this connection mention should be made of the improvements in the 

 technique for demonstrating chromaffin tissue which have been devised by 

 Dr. Wislocki, whereby the presence of this tissue can be determined with 

 greater clearness and precision. With this technique he has been able to show 

 the presence of chromaffin bodies of macroscopic size in the retroperitoneal 

 tissue of a number of mammals (opossum, squirrel, guinea-pig, and monkey) 

 in which previous observers had failed to find them. 



NERVOUS SYSTEM. 



Development of Medial Wall of Forebrain. 



The cerebral vesicles in the human embryo exhibit on their medial wall a 

 transitory fissuration, the significance and even the existence of which has 

 been the subject of much controversy among embryologists and neurologists. 

 Dr. Marion Hines, using the material in the University of Chicago collection 

 together with our material, has been able to give a clear account of this 

 phenomenon. She has shown that an arcuate or hippocampal fissure does 

 exist and that it is delimited by a characteristic histological morphology of 

 the neural wall. She has discovered that at a certain stage in development 

 it is coextensive with the hippocampal primordium and that, as cortical 

 differentiation proceeds, that portion of it which lies anterior to the velum 

 transversum disappears. Posterior to the velum, however, it persists as the 

 adult fissura hippocampi. The whole hippocampal region, together with the 

 adjacent parts of the telencephalic vesicle, is included in this study, which 

 will make it of fundamental value to the brain anatomist. 



