The Origin and Development of the Lymphatic System. 13 



which has already given the suggestion of a lining of flattened cells 

 for blood capillaries. Strieker saw clearly that the wall of the capil- 

 lary was of living protoplasm, bnt was confused in regard to whether 

 the blood stream was inter- or intra-celhilar. He was perplexed also 

 in regard to the existence of cells or not, since he was dealing with 

 the growing tip, which we now know to be a syncytium. This idea 

 occurred to Strieker, as is plain in these words, " Dass bei dem Auf bau 

 von Kapillargefassen ueberhaupt Zellen mit einander verschmelzen, 

 und dass solche Verschmelzungsspuren spater einmal durch Silber- 

 niederschlage kenntlich werden konnen, lasst sich ferner auch nicht ' 

 leugnen." Strieker also noted the sprouts of blood vessels as indi- 

 cating their method of growth. 



I have already taken up the fact that von Eecklinghausen's work 

 on the endothelium of lymphatic vessels, studied by means of the 

 silver nitrate method, settled the question of the cellular nature of 

 the lining of lymphatics, especially in connection with the analysis of 

 the work by His, who had regarded lymphatics as vessels without 

 walls (44, p. 229), and saw by a thorough study of preparations made 

 by the silver method that lymphatics were lined throughout by endo- 

 thelium. 



In 1867 Langer (75), as a conclusion to a series of studies on the 

 lymphatic system in amphibia, published a study of the lymphatics 

 in the tadpole's tail. He was able to make complete injections of the 

 blood vessels and the lymphatics and gives a most interesting analysis 

 of specimens as observed in alcohol from the standpoint of weighing 

 the evidence on the method of growth. He describes the uninfected 

 capillary as often appearing to have a single contour, while the injected 

 one had the complete wall. He could not find in the alcoholic speci- 

 men the tiny processes previously described, in the living form. He 

 noted, however, the larger sprouts, the loops and blind processes, and 

 says that the nuclei are definitely within the contour of the -wall of 

 the capillary, so that he makes the distinction between the vessel and 

 the surrounding tissue. He concludes that the various forms of the 

 processes must indicate the process of centrifugal growth for the lym- 

 phatic capillary as well as for .the blood capillary. 



4gain in 1873 the growth of the lymphatics and blood vessels by 

 the method of sprouting was observed in the tadpole's tail and very 

 clearly described by Eouget. By the use of curare he was able to keep 

 the larva still. He also emphasizes the great number of tiny filaments 



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