10 DEVELOPMENT OF THE SYSTEMIC LYMPHATIC VESSELS 



our knowledge of the genesis of the mammalian lymphatic 

 system. 



The results so far obtained, and the views based thereon, may, 

 with inclusion of the older work on the subject of vertebrate 

 lymphatic development in general, be briefly summed up as 

 follows in the form of short theoretic statements: 



I. The lymphatic system is developed independently of the 

 blood-vascular system. It is formed by the confluence of inde- 

 pendently developed mesenchymal spaces, and, in case of the 

 avian thoracic duct, by canalization of preformed solid strands 

 of differentiated mesenchyme. 6 - 6 > 7 



The works of Brachet and the combined researches of Brachet 

 and Swaen, 8 in their relation to the interpretation of lymphatic 

 development, also support the independent origin of the lymph- 

 atic system from the mesenchyme. 



The interesting observations of Marcus on the development and 

 organization of the lymphatic system in Hypogeophis 9 place the 

 conclusions of this investigator in regard to the genesis of lym- 

 phatic structures in this general division, with the addition of the 

 conception of the coelomata as primary lymphatic spaces (vide 

 infra, pp. 25 and 26), and the phylogenetic derivation of the 

 peripheral lymphatic system from the same. 



8 Budge: "Ueber ein Canalsystem im Mesoderm von Hiihnerembryonen." 

 Arch, fiir Anat. und Phys., Anat. Abth., 1880, s. 320. "Untersuchungen iiber 

 die Entwicklung des Lymphsystems beim Hiihnerembryo." Arch. f. Anat. u. 

 Phys., Anat. Abth., 1887, s. 59. 



6 L. Sala: "Sullo sviluppo del cuori linfatici e del dotti toracici nell' embryone 

 di polio," Ricerche fatta nel Laboratorio di Anatomia Normale della R. Univ. 

 di Roma, vol. vii, p. 263-269, April, 1900. 



7 G. Lovell Gulland: "The Development of Lymphatic Glands", Jour. Path, 

 and Boot., vol. ii, 1894, pp. 447-485. 



8 A. Brachet, "Recherches sur le developp. du coeur, des premiers vaisseaux 

 et du sang chez les amphibiens urodeles," Arch, d'anat. microscopique, ii, 1898. 

 "Recherches sur 1'origine de 1'appareil vasculaire sanguin chez les amphibiens," 

 Arch, de Biologic, xix, 1903. 



A. Swaen et A. Brachet, "Etude sur les premiers phases du developp. des 

 organs derives du mcsoblast chez les poiissons teleostiens," Arch, de Biologie, 

 xvi, 1899-1900. 



9 H. Marcus, "Beitrage zur Kenntnis der Gymnophionen; II. Ueber interseg- 

 mentale Lymphherzen, nebst Bemerkungen iiber das Lymphsystem," Morphol. 

 Jahrbuch, Bd. xxxviii, Heft 4, 1908. 



