428 Mr. Lawson Tait on the 



at as low a pressure as 55 millims., with a nozzle only 1 millim. in dia- 

 meter ; yet at a pressure of 350 millims. I have not produced a rent in , 

 the surface of the cord, though I have produced numerous extravasations 

 into the alveoli and into the neighbouring columns. The appearances 

 when these canals are distended are well shown in several of the draw- 

 ings, but especially in Plate 11. figs. 5, 6, and Plate 12. fig. 14, in the 

 first of which they are seen to run up close to the muscular coat of the 

 artery. Transverse and longitudinal sections of the same piece of the 

 cord show that they are stellate in every plane, and that they intercom- 

 municate in every direction; but their processes are slightly longer in 

 the long axis of the cord than in any other. This, however, is not con- 

 stantly evident. 



Recklinghausen regards these canals as wall-less spaces between the 

 anastomosing cells, simple interspaces in the connective-tissue basis 

 substance (" Ausgrabungen in der Bindegewebs-Grundsubstanz ") ; but 

 that this is not so my own observations, substantiating those of Koster, I 

 think completely established. It is best proved by preparations of the 

 termination of the injected district, where the blue colour may be seen 

 running into the processes of the so-called stellate " connective-tissue 

 corpuscles," contrasting with the complete occupation by the colour of 

 every thing but the alveoli*. It is in these alveoli exclusively that I have 

 found the round migratory cells. 



Henle thinks that the anastomosing cells may be the foundation plan 

 for blood-vessels (" Gef assanlage "), such as are seen in the umbilical cords 

 of all mammals but man. So far, however, as I have yet seen the vessels 

 which extend over the mammalian cord are chiefly on its surface, as I 

 have already mentioned they are to a limited extent at the foetal inser- 

 tion of the human cord ; but this point is one for further research. 

 It is scarcely possible, however, to regard a system of canals which 

 constitutes the ivhole tissue of the cord as a representative of blood-vessels, 

 otherwise it must somewhere be seen as an almost erectile tissue. 



Fohmann has asserted that he has injected a complete system of lym- 

 phatic vessels in the cord by quicksilver; and though Virchow thinks 

 that his material has permeated the alveoli, and Hyrtl that his lymphatics 

 are mere chasms in the tissue, I think it possible that he really has 

 injected these canals, but that from his inability to make sections which 

 would retain the quicksilver in the tissue, he has not demonstrated the 

 facts of his system. This difficulty is obviated by the use of size and 

 Berlin blue. 



Staining with silver lactate (1 in 800, with slight excess of lactic acid) 

 leaves the canals as clear white spaces (Plate 11. fig. 3), but gives a decided 

 brown edge to them, which shows that they are walled. Their general 

 appearance after this treatment closely corresponds to that seen after 



* This is also shown in silver-stained sections (Plate 11. fig. 3), where the walls seem 

 indicated by an increase of colour. 



