Earliest Blood Vessels in Anterior Limb Buds. 283 



The first publication from this laboratory, referring to the injec- 

 tion of embryos, was made in 1900, in the research by Flint' on 

 the blood-vessels of the adrenal. Injections were used extensively 

 by Sabin^ in the study of the development of the lymphatic system, 

 and in her first publication on this subject (1002), mention is made 

 of the injection of the blood vascular, as well as lymphatic systems, 

 in young pig embryos. 



In 1904, Professor Mall's "Development of the Blood- Vessels of 

 the Brain in the Human Embryo"^ appeared, and in it he reported 

 briefly some of the methods and results of the injection of embryos, 

 which he had been conducting for some time. His paper outlined 

 a method of obtaining splendid double injections. India ink was 

 injected into the liver and being taken to the pulsating heart, driven 

 by the latter through the arterial tree. The embryo was then cooled 

 and the beat of the heart arrested, whereupon a second injection by 

 way of the liver now filled the veins. At other times single injec- 

 tions of the arteries, or of the veins, were made by the same method, 

 i. e., through the liver, and these were, in many cases, remarkably 

 complete. Thus the feasibility of demonstrating all the chief ves- 

 sels of the embryonic venous or arterial system became an estab- 

 lished fact. 



But until recently, though injections of most of the vascular tree 

 had been secured, it was necessary to perfect the method so that 

 an approximately complete filling of all the body's capillaries could 

 be secured, and so that even the very youngest embryos could be 

 successfully treated in this way. 



Many hundred trial injections, with living embryos under the 

 best conditions obtainable, have evolved methods delicate, and yet 

 effective enough, to successfully fulfil these two conditions. I 



Tlint J. M. "The Bloodvessels, Angiogenesis, Organogenesis, Reticulum, 

 and Histology of the Adrenal." Contributions to the Science of Medicine, 

 dedicated by his pupils to William Henry Welch. Baltimore, 1900. Pp. 1.53-228. 



^Sabin, F. R. "On the Origin of the Lymphatic System from the Veins 

 and the Development of the Lymph Hearts and Thoracic Duct in the Pig." 

 Amer. Jour, of Anat., Vol. I, 1902, pp. 367-391. 



^Mall, F. P. "On the Development of the Blood-Vessels of the Brain in the 

 Human Embryo." Amer. Jour, of Anat., Vol. IV, 1904. 



