30 
HEMOLYMPH NODES OF THE SHEEP 
way, and concluded that the vascular system of hemal nodes, i. e., of 
nodes having no lymphatics and containing much blood, is a closed sys- 
tem, as is the case in lymph nodes, v Schumacher based this conclusion 
on the fact that the injection mass by no means always enters the paren- 
chyma of hemal nodes, and that it occasionally does so in lymph nodes. 
Hence he rules out all the instances where injection mass is found outside 
of the circulation , but only denies the existence of a regular communica- 
tion between the blood vessels and blood spaces., 
Attention was called to the fact that there is a decided difference in 
the frequency and nature of these extravasations in hemal nodes, and 
that microscopical evidence of the communication between the venous 
sinuses or radicles and the parenchyma is not wanting. Hence, in short, 
the circulation of hemal nodes is similar to that of the spleen, and not 
to that of lymph nodes. I cannot believe that the openings in the venous 
sinuses are purely accidental, or that all the erythrocytes entered the par- 
enchyma of hemal nodes at places which lymphocytes had previously 
weakened. Moreover, I fully agree with Weidenreich in regarding the 
spleen as only a higher ( ?) type of hemal gland. Schmalz, too, thought 
hemal glands may be designated accessory spleens. 
Since it has been entirely impossible to demonstrate a direct com- 
munication between the arteries and the blood islands or spaces, it ap- 
pears to me that these communications between the lacunae and the par- 
enchyma must be regarded as affording the only means of entrance of 
the leucocytes of the node into the circulation ; except, of course, by pas- 
sage through the wall, as in lymph nodes, and through a free communica- 
tion between the peripheral blood spaces and the veins, which occasional- 
ly exists in depleted nodes. That this statement necessarily needs modifi- 
cation to suit the conditions existing in seriously depleted nodes, is evi- 
dent, of course. Furthermore, the fact that the blood spaces — blood 
islands including the peripheral blood space — always contain reticulum 
and have no bounding wall, while the venous lacunae and venous spaces 
never contain reticulum but always have a definite wall, also seems to 
imply that the latter represent definite permanent channels whose endo- 
thelium cannot well be co-extensive with the reticulum, and which are 
in direct relation with the veins. Hence the conclusion that all the 
lymphatic tissue and the included blood islands and blood spaces lie 
wholly outside the continuous circulatory system as a rule, seems entirely 
justified. But, whatever the relation of these structures to the circula- 
tion of hemal nodes, being inconstant and transient, they manifestly 
cannot be regarded as forming an integral part of a system of con- 
