Anatomy of the Umbilical Cord. 427 



examination and treatment of tissue which has been subjected to hard- 

 ening reagents so unsatisfactory that I have quite discarded it. 



All my sections are made by the freezing process (described in Hum- 

 phrey and Turner's Journal for May 1875), so that sections of the 

 perfectly fresh cord of about -g-J-y of an inch in thickness have been 

 examined. These have been subjected to various treatments — as simple 

 clearing by glycerine, destruction by acetic acid, staining by silver lactate, 

 and by my various indifferent staining-fluids, hematoxylin, litmus, cab- 

 bage, &c. (also described in Humphrey and Turner's Journal). 



My injecting-apparatus is so arranged that it acts automatically when 

 set at work. The tissue injected and the whole apparatus is surrounded 

 by a current of warm water, the temperature of which is registered. 

 The injecting force is supplied by compressed air admitted directly to 

 the surface of the injecting-fluid, and the pressure is registered by a 

 manometer. The nozzles used vary in diameter from 1 to 4 millims. 

 The fluid used is a ten-per-cent. mixture of Seitels's Berlin blue sus- 

 pended in firm size. This does not stain the tissue because it is not in 

 solution, yet its granules are too small to be seen by any power of lens 

 in my possession! That it is not in solution is certain from the fact 

 that it is completely removed from the fluid by adding some albumen 

 and boiling. Similar but not so satisfactory results may be obtained by 

 Davies's granular carmine ; but here the granules are too large to enter 

 the canals, save under such pressure as produces frequent extravasation. 



One disadvantage of the Berlin blue is that it contains a little free 

 acid, and must do so to remain visible. After a short time this acid 

 destroys the colouring of the stained nuclei ; so that, save in an almost 

 perfectly fresh specimen, it is impossible to demonstrate the relations of 

 the nuclei to the canals when distended by the injection. 



The method of injection of these canals is apparently very rough. It 

 consists simply in inserting a small nozzle superficially into the substance 

 of the cord over and parallel with the course of a vessel, tying it in, and 

 injecting under a low pressure of 50 or 60 millims. of mercury. 



Schweiger-Seidel made the very obvious objection to this (Reckling- 

 hausen's) method that any appearances presented by it would be simply 

 those of extravasation. Such was my own belief when I first tried it on 

 the cord ; but very short experience showed me that the result was a 

 regular and uniform injection of a system of canals, and that extravasa- 

 tion was very rare and always limited to the immediate neighbourhood 

 of the wound in the cord. "With the whole apparatus at a temperature 

 of 47° and a pressure of 60 millims., I have injected a column of the 

 cord for a distance of 9 inches in about half an hour. The injection 

 travels rather more rapidly in the direction from the child to the placenta 

 than in the opposite direction. 



I have repeatedly seen minute streams of the blue injecting fluid 

 flowing from the surface of the cord into the water surrounding it, even 



2i2 



