DISTRIBUTION, OCCURRENCE AND APPEARANCE 
I I 
lated blood. Exposure of fresh hemolymph nodes to gaseous hydrogen 
sulphide in pure or mixed form, or to weak or concentrated solutions of 
the same in water, in alcohol, and to an ammonia-alcohol mixture con- 
taining hydrogen sulphide would, on the contrary, invariably result in a 
rapid change to an intensely black color. It was also noticed that ex- 
posure of cut nodes in water saturated with hydrogen sulphide caused a 
more rapid change to a deeper black than exposure in a solution of 80 
per cent alcohol similarly saturated. Since the latter solution con- 
tains much more hydrogen sulphide than the former, it is appar- 
ent that the slower and less pronounced color change in nodes immersed 
in it is probably due to the effect of shrinkage and hardening, and per- 
haps also to the dehydrating effect of the alcohol. If they were exposed 
to the action of diluted instead of concentrated gaseous hydrogen sul- 
phide, a very gradual change to green followed that to black, thus giving 
the nodes a grayish color, as described by Warthin [36]. Furthermore, 
if the freshly cut surface of a node was thus exposed, these changes were 
much more rapid, and the green was frequently so deep that it simulated 
black. Solutions in water of hydrogen sulphide and of the yellow am- 
monium sulphide, in various concentrations had a similar action. How- 
ever, if immersion of the nodes in a solution of sulphide, free from oxy- 
gen, was complete, no change from black to green took place at all. The 
black color remained permanent, and was retained in the alcoholic hard- 
ening solutions, as well as in all later processes. These facts suggest, of 
course, that the change from black to green is indeed an oxidation change 
of some sort; which conclusion is further confirmed by exposure of 
nodes to pure hydrogen sulphide, with subsequent exposure to pure car- 
bon dioxide or to oxygen. Nodes kept in pure hydrogen sulphide, or 
subsequently exposed to carbon dioxide, remained black for days. 
As in the case of the color changes due to oxygen, the color change 
due to these pure gases or mixtures of them was a very superficial one, 
even after prolonged exposure — for six to eighteen hours — to either 
gaseous hydrogen sulphide or to a solution of the same. Such exposure 
never resulted in a color change beyond the depth of one or two milli- 
meters, even on the surface of a freshly-cut node. At greater depths 
into the node the original color was retained, even for twenty-four hours 
or more, until maceration and putrefactive changes produced the usual 
results. The same was true regarding the apparently permanent green 
color which followed the change to black. If fresh nodes or pieces of 
the same were immersed in 95 per cent alcohol saturated with hydrogen 
sulphide, they would undergo the usual color changes; but after weeks 
