The Origin and Development of the Lymphatic System. 11 



the work of Platner (106) and of Prevost and Lebert (108). Platner 

 described the growth of capillaries as seen in the living tadpole's tail. 

 He analyzes Schwann's idea of the addition of cells as necessarily 

 merely an inference from the appearance of the vessels in one stage, for 

 when actually seen growing new cells are never added on. He says 

 that rather each new vessel is a process of a preceding one and 

 describes these processes as long, thin Auslaufer, which form loops 

 and soon show a double contour. He says that the tiny processes 

 never contain nuclei and are not cells, so that the interpretation of 

 Schwann of the addition of cells could not possibly hold. Platner 

 says that the same process of growth in the living tadpole had been 

 observed by Prevost and Lebert. Indeed, in the same year (108) they 

 published a series of four papers, in which they describe the growth 

 of capillaries, not only in Batrachians, but more in detail in connec- 

 tion with the blood islands in the chick. They definitely use the term 

 centrifugal growth and describe the process in the following graphic 

 terms (p. 239) : "Les vaisseaux poussent des saillies laterales par 

 decollenient partiel des lamelles du feuillet vasculaire, saillies plus 

 ou moins arrondies ou pointues, allongees, formant des especes 

 d'eperons qui souvent finissent par se rencontrer, provenant de deux 

 cotes differents, et etablissent ainsi des vaisseaux de communication." 

 They thought that the processes or " spurs " were for the most part 

 hollow from the start and state that the larger vessels grew by the 

 same method as the smaller. 



In 1846 Koelliker published two papers (67 and 68), in one of 

 which he announced the discovery of lymphatic capillaries in the 

 tadpole's tail (67). He described the characteristic differences as seen 

 in the living form between the two types of capillaries, the irregulari- 

 ties and more numerous processes of the lymphatics as well as their 

 connection with the superior and inferior caudal lymph trunks. In 

 the other paper he gives a most valuable analysis of the views of the 

 early embryologists, Wolff, von Baer, Eeichert and others on the prob- 

 lem of the growth of vessels. He takes up the various views of growth 

 (p. 118) which were then being discussed, namely, growth (1) by the 

 addition of unbranched cells, or (2) by branched or stellate cells, 

 or (3) by spaces hollowed out by the force of the heart beat, or (4) 

 from spaces produced by fluids in the tissues as well as (5) by the 

 then new work of Platner, Prevost and Lebert, showing centrifugal 



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