464 Drs. Herring and Simpson. Relation of the [May 31, 



marked. Others failed to show the intracellular channels. The cells of the 

 monkey's liver appear, therefore, to be injected less readily than those of the 

 other animals investigated, and for their injection comparatively high 

 pressures were necessary. But whether this result is due to the fine calibre 

 of the channels, or to some unknown accidental circumstance, we are unable 

 to say. 



Three birds, a common fowl and two pigeons, were injected from the right 

 aortic arch at pressures of 100 and 130 mm. Hg. Many of the liver cells 

 contain fine threads of carmine gelatine, with occasional rounded or irregular 

 accumulations. In these birds, as in the monkey, the intracellular passages 

 are very fine (fig. 9). 



From what has been stated about the pressures of the injections employed, 

 it will be seen that they are not excessive, and many of them might quite 

 well be exceeded by that of the blood during life. When the inferior vena 

 cava was ligatured before the injection pressure was cut off, the pressure in 

 the liver vessels must have risen considerably, but even in these cases, when 

 the injection was made from the aorta, the mass, with the exception of that 

 entering by the hepatic artery, has already traversed one set of capillaries 

 before it reaches the liver. As has already been insisted on, some of the best 

 injections were made with the inferior vena cava open. In the rat an aortic 

 pressure of 80 mm. Hg, with free escape of the injection mass from the 

 inferior vena cava, yielded one of the best of our preparations (fig. 4), the cells 

 being injected uniformly throughout the organ. In one cat a pressure of 

 20 mm. Hg in the portal vein, with free escape from the inferior vena cava, 

 also yielded a typical injection of the cells. In a dog, with hepatic artery- 

 and portal vein tied, there was sufficient backward flow to inject the cells at 

 the central parts of the lobules, although the inferior vena cava was open in 

 the thorax. 



The appearance of injection material in the liver cells cannot therefore be 

 ascribed to excess of pressure in the blood-vessels. The character of the 

 injection in the cells, too, as was pointed out by Schafer, is against any such 

 supposition. In many places there are definite fine channels continuous with 

 the lumen of the blood-vessel, forming a network within the cell. Dilatations 

 on the network are often seen. These are probably vacuoles in the cytoplasm, 

 and may be more distended with increase of pressure, but the typical network 

 is best seen when a moderate pressure only has been employed. 



The presence of injection within the cells is not the result of vital activity 

 of the cell protoplasm. The circumstances of its occurrence are against this 

 supposition, as well as the fact that the cells can be injected a considerable 

 time after the death of the animal. Perfusion of large quantities of chloro- 



