DISTRIBUTION, OCCURRENCE AND APPEARANCE 
13 
ly, it might still be true that the change from red to black which is pro- 
duced by exposure of nodes to hydrogen sulphide, although not directly 
attributable to, might yet be accompanied by the presence of an excess 
of iron in hemolymph nodes. Although Warthin's conclusion regarding 
the excess of iron in hemal nodes relies partly upon these color changes, 
it is interesting to report that the fresh blood of any animal turns black 
almost instantly on exposure to hydrogen sulphide. Evidently, then 
according to Warthin's reasoning the blood of a number of domestic 
animals must contain more iron even than the hemolymph nodes of these 
same animals : a conclusion in direct contradiction to that of Warthin. 
Moreover, it was found that not only the blood, but also the spleen, 
muscle, liver, blood vessels — in fact any fresh vascular tissue — would 
undergo identically the same color changes, and do so even more rapidly 
in some cases than the hemolymph nodes themselves. From these obser- 
vations it is clear then that the hemolymph nodes very likely undergo 
these color changes when exposed to hydrogen sulphide, simply because 
they are very vascular; and not necessarily, as assumed by Warthin, 
because they contain an excess of inorganic iron. To be sure, Warthin 
may be correct in assuming that it is an iron compound which produces 
these changes. That is not denied here. What concerns us is whether 
or not these color changes necessarily indicate a greater content of iron 
on the part of the hemolymph nodes. That this is not the case the facts 
cited seem to establish beyond all question. To be sure, if, as has been 
claimed, hemolymph nodes are the seat of blood destruction, with result- 
ing decomposition of blood pigment, it is possible, of course, that they do 
contain a large or even a larger amount of iron ; but the above action of 
hydrogen sulphides is manifestly not a satisfactory criterion. Moreover, 
in another article Warthin [32] contradictorily enough reported that he 
found but a slight or no reaction for hemosiderin in hemolymph nodes. 
The latter observation, which is contradicted by some investigators, 
agrees entirely with the findings of the writer; and it seems possible, 
although perhaps not entirely probable, that differences in the freshness 
of the material may at least in some measure account for these discrepan- 
cies, v Schumacher [27] also emphasized the rare and sparse occurrence 
of pigment in the hemolymph nodes of sheep. 
Although there are great variations in the quantity of blood con- 
tained in hemolymph nodes, their vascularity, as judged by external 
appearances, did not seem to be affected by the rate or thoroughness of 
bleeding during slaughtering. In sheep which were bled slowly from 
one carotid or jugular only, or in others which were bled rapidly from 
