ON" THE DEVELOPMENT OF THE BLOOD-VESSELS OF THE 

 BRAIN IN THE HUMAN EMBRYO. 



FRANKLIN P. MALL. 



From the Anatomical Laboratory of the Johns Hopkins University. 



With 3 Double Plates and 4 Text Figures. 



During the past year, while studjdng sections through the heads of 

 the embryos in the collection at this laboratory, it was noticed that 

 in some of the specimens the blood-vessels were unusually well marked, 

 for they were well distended with blood. This natural injection made 

 it possible to reconstruct the blood-vessels in a satisfactory manner 

 down to the capillaries. At the same time I obtained from Mr. Brodel. 

 a number of embryos' brains in which the arteries had been injected 

 with Prussian blue, which, together with numerous embryo pigs injected 

 alive or immediately after death, form the basis of this study. 



TABLE OF EMBKYOS STUDIED. 



"The blood-vessels of five human embryos were reconstructed from 

 serial sections, and eight older embryos which had been injected were 

 dissected. The brains of pigs which had been injected with India ink 

 proved to be of great value to control the studies of the human. It is 

 quite easy to make single or even double injections of young embryos 

 by injecting them either before or after death, or both. In case India 

 ink is injected into the liver of a live pig with a hypodermic syringe, the 



American Journal of Anatomy. — Vol. IV. 



