THE DEVELOPMENT OF THE LYMPHATIC XODES IN THE 

 PIG AND THEIR EELATION TO THE LYMPH HEARTS. 



BT 



FLORENCE R. SARIN. 

 From the Anatomical Laboratory, Johns Hopkins University. 



With 17 Text Figures. 



Notwithstanding the numerous investigations on the lymphatic nodes, 

 there are many points in regard to their structure and development in 

 which our knowledge is not yet clear.' For example, such a fundamental 

 question as the relation of the nodes to the lymphatic system as a whole 

 and to the vascular system, in other words, the prohlem of general 

 morphology: or, more special questions in regard to the nodes them- 

 selves; primarily the existence of a structural unit; and secondarily the 

 relations of the endothelium of the channels to the reticulum within the 

 node, whether the channels are open or closed, and the origin of the 

 lymphocytes. 



In regard to the problem of general morphology, we have previously 

 shown " that the lymphatics are modified veins. They develop as blood- 

 vessels do, by the budding of endothelial cells, and the direction of their 

 growth is determined by the arteries and veins. In the lymphatic sys- 

 tem there develop four lymph hearts which pulsate in the amphibia; but 

 in the mammalian forms, at least in pig and human embryos, have no 

 muscle in their walls. These lymph hearts drain the body, that is to 

 say all the lymph passes through them before entering the veins. It 

 will be shown in the present paper that the first lymph nodes in the body 

 develop from the lymph hearts. That is, the organ which was a pulsat- 



^ During the past eleven years, there have been four extensive researches 

 on the development of lymph nodes by Gulland, Saxer, Retterer, and Kling. 

 Each of these authors has reviewed the literature. Gulland, Journal of 

 Pathology and Bacteriology, Vol. 2, 1894; Saxer, Anatomische Hefte, Bd. VI, 

 1896 Retterer, Journal de L' Anatomie et de La Physiologie, 1901 Kling, 

 Upsala Lakareforenings Forhandlinger, 1903, and Archiv f. mik. Anat. u. 

 Entwicklungsgeschichte, Bd. 63, 1904. 



^Sabin: American Journal of Anatomy, Vol. I, 1902. 

 American" .Tocrnal of Anatomy. — Vol. IV. 



