Florence E. Sabin 3G9 



from the side of a duct appears a bud which is at first solid, but soon 

 has a lumen. The lumen becomes larger, while at the same time the 

 bud advances until it reaches a second duct. It opens into this duct 

 by a process of absorption of the endothelium, and at the point of 

 junction a valve is made. These points are beautifully seen in injected 

 specimens for the larger duct forms, as Kanvier says, a collarette for 

 the smaller. Thus he says the ducts grow from centre to periphery, 

 while the valves necessarily open in the opposite direction. He says 

 that as soon as lymphatics can be recognized in mammals they are 

 furnished with valves. He also worked on frogs and described injec- 

 tions of the subcutaneous lymph sacs. From these sacs fluid can be 

 made to run centrally to one of the lymph hearts and thence to the 

 vein, and peripherallv to minute ducts in the web of the feet. Ean- 

 vier states that these small ducts develop from the great lymph sacs. 



His general conception of the lymphatic system is that it is a great 

 gland of which the lymphatic capillaries correspond to the secreting 

 portion, while the lymphatic ducts are the excretory canals. He says 

 that the lymphatic system may be considered as a great vascular gland 

 which takes its origin en?l)ryologically in the venous system and pours 

 into the veins the product of its secretion which is lymph.' 



Eanvier's great contribution to the study of the lymphatic system 

 is the discovery of the fact of the growth of the ducts by budding in 

 contradistinction to the generally accepted theory that the lymphatic 

 system develops out of tissue spaces. Gulland * states this theory 

 clearly as follows: The fluid of the blood exudes from the veins into 

 the tissue spaces which gradually dilate, flow together and form the 

 first lymphatic ducts. The walls of these ducts are made from the 

 connective tissue which becomes compressed around them, and the 

 ducts subsequently open into the veins. The most recent statement 

 of this theory is that of Sala.' He describes the development of the 

 lymph hearts and the thoracic duct in the chick as follows: That the 

 first trace of the lymphatic system is the appearance of lymph hearts 

 or spaces in tlie mesenchvrae just lateral to the caudal myotomes. 

 These spaces flow together and join the thoracic duct, which forms 

 as two cords of mesenchyme cells which extend from the level of the 

 thyroid glands to the level of the coeliac axis. In the centre of these 



sRanvier: Comptes Rendus, Tome 121, 1895, p. 1109. 

 ^Gulland: Jourual of Pathology and Bacteriology, Vol. II, 1894, p. 406. 

 5Sala: Ricerche n. lab. di anat. norm. d. r. Univ. di Roma, Vol. VII, 1900, pp. 

 263-'269. Reviewed in Archives Italiennes de Biologic, Tome 34, 1900, p. 453. 



