CLASSIFICATION 
59 
ation of group I into group 2, and also regarded a retransformation prob- 
able. 
Baum [ 1 ] recognized two classes of hemolymph nodes : those with- 
out lymphatics, which he designated lymphoid hemal nodes ; and those 
with afferent and efferent lymphatics, or lymphatic hemal nodes. 
Weidenreich was the first to demonstrate experimentally that the so- 
called hemolymph nodes in the sheep are wholly independent of the lym- 
phatic system, thus, in a measure, justifying Drummond's supposition that 
they are organs sui generis. This statement of Weidenreich has been 
abundantly confirmed by the present investigation. Consequently there 
would seem to be no need for any more than two classes of lymphoid 
organs — lymph and hemal nodes. That not all hemal nodes varying in 
structure quantitatively can or should be classified separately is evident, of 
course; and such an elaborate classification as suggested by Lewis [13] 
and Warthin [32 and 35] is unwarranted, confusing, and certainly un- 
scientific. The many structural variations in hemal nodes to which atten- 
tion has been directed, no more justify separate classification than would 
the manifold variations in external form of such an organ as the liver, for 
example. 
Neither the term hemal nor hemolymph node is wholly satisfactory or 
an appropriate one, however, for not all hemal nodes have an appreciable 
quantity of blood in the parenchyma; although they are intercalated in 
the vascular, and not merely in the venous system, as has been variously 
stated. Lymph nodes, on the contrary, are of course not, as the term 
would imply, only in relation with the lymphatic system. Hence lymph 
nodes are virtually the only true hemolymph nodes, for they alone have 
both lymphatic and vascular circulations wholly independent of each other. 
The term hemoadenoid would be clumsy and equally confusing as hemo- 
lymph ; and while the term splenic is undoubtedly the most preferable and 
proper, in spite of the absence of Malpighian corpuscles in almost all 
hemal nodes of the s'heep, the writer does not feel justified in introduc- 
ing another term and thus adding to the confusion which already 
exists. Hence the retention of the term hemal node seemed commend- 
able. 
A subdivision of hemal nodes into active and inactive, while empha- 
sizing certain prominent physiological differences, would not be exclusive 
either, for there probably are very few nodes in which functional processes 
are wholly in abeyance, even when the nodes are being rapidly depleted 
of lymphocytes and converted into a sac of blood. Moreover, we know 
but little regarding their origin, function and final fate. It is evident, 
of course, that in the case of depleted nodes, poliferation may nevertheless 
