LYMPHATIC AND VASCULAR RELATIONS 
23 
to the differences in pressure and to interference with the architecture of 
the node by the puncture in case of direct puncture injections, as well as 
to other things to be discussed presently. Unfortunately, none of the 
nodes injected from the aorta had a sufficiently definite peripheral 
(sinus) blood space to afford good evidence regarding its relation to the 
arteries. That the injection mass could have entered the peripheral 
(sinus) blood space follows, however, from the fact that the latter al- 
ways contains more or less blood. Hence both it and the central blood 
spaces must, to be sure, communicate in some manner with the vascular 
system, even if not directly with it as a rule, or with the artery. 
The most significant result obtained from these injections was that 
the so-called venous lacunae or radicles could generally be injected from 
both the vena cava and from the aorta. It is true that these injections 
were not of equal completeness, and also varied in certain other minor 
respects; yet the above fact seems to demonstrate conclusively that the 
venous lacunae, or true venous sinuses of the hemal nodes of the sheep, 
occupy a position intermediate between the veins and the arteries, and 
hence bridge a gap between them. However, as already stated, the fact 
that the blood spaces are more easily injected by puncture than from the 
aorta, can readily be explained by the fact that higher pressures were 
undoubtedly used, that a more direct and sudden entrance of the injec- 
tion mass is effected, that the architecture of the node may be seriously 
disturbed, and that the needle may happen to stop in the parenchyma, in 
the case of direct puncture injections. Moreover, in case of injections 
from the aorta the injection mass, which enters slowly through the 
artery, can pass directly onward into the wide venous lacunae and large 
veins, without producing any appreciable back pressure in them, because 
of the difference in calibre between the arterial capillaries and venous 
sinuses. Hence the injection is likely to be incomplete. That the injec- 
tion masses or the pigment, are generally found in the venous lacunae 
or true sinuses, and not in the blood islands and spaces, is explained by the 
fact that the former are usually empty spaces, with permanent walls 
which, although usually in a state of total or partial collapse, are direct- 
ly connected with the arteries, and hence offer far less obstruction to the 
entrance of the injection mass than the blood spaces. The latter are tra- 
versed by reticulum and are filled with blood which has no easy and free 
means of escape. Furthermore, the communication between the venous 
lacunae and blood spaces is, as a rule, only an indirect one. 
The great irregularity in shape of the injection masses and the pig- 
ments, in both arterial and venous injections, somewhat suggested extrava- 
sations. This was probably due to the necessarily incomplete nature of 
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