GENESIS OF INTERMEDIATE FORMS 
57 
Another explanation for the occurrence of reddened lymph nodes 
lies in the old observation that such a wide and direct open communica- 
tion between the afferent and efferent lymphatics of a node may exist 
directly through the peripheral sinus, that the active lymph current is 
largely, even if not wholly, limited to the latter. Under such circum- 
sances there would be a slow lymph current in the interior of the node, 
with consequent accumulation of blood cells as a result of stasis. That 
nodes with such circulatory conditions exist is beyond question, for the 
varying rate with which suspensions of India ink traverse a node is quite 
striking. Were it not for the existence of such large peripheral sinuses, 
a great deal more difficulty would also be experienced in injecting a series 
of successive nodes from the most peripheral one, and of accounting for 
the ease with which the thoracic duct, even up to its entrance into the 
vein, can occasionally be injected from the pad of the foot in the cat. In 
several instances this was accomplished with but a small fraction of a 
barrelful of India ink contained in a hypodermic syringe of 2% cc. vol- 
ume. These observations confirm the inferences of v Frey and Donders, 
and also the observations of Richter in the pig. 
In looking about for an explanation for the reddening of lymph 
nodes and the presence of blood in the sinuses, Vincent [29] said : "I have 
not so far studied the blood supply to these glands by means of injections, 
nor have I succeeded in finding the blood vessels in direct communication 
with the iymph' sinuses of the gland; but from the large number of red 
corpuscles sometimes found in them, I am convinced that there must be 
such communication." It will be remembered that Meckel Jr. and Sr., 
Lindner, Fohmann, Lauth, and, of course, Lippi, also believed in the ex- 
istence of such communications, and that Lewis [13] claims to have 
abundantly confirmed such occurrences by observation. While making 
thousands of injections of lymph nodes, no evidence for the existence 
of such communications, whose accidental existence is therefore not de- 
nied, was obtained in the sheep. However, in young cats, in which the 
mesenteric lymph nodes are very tender, both veins and lymphatics were 
not infrequently injected by puncture from a node. In most instances 
the lymphatics were injected first, and then the veins. Moreover, in 
guinea-pigs such results are far easier to obtain, and not infrequently 
the injection of veins and lymphatics is practically simultaneous. Never- 
theless, a little experimentation proves conclusively that these results are 
obtained only because the tender nodes are distended by the injected mass, 
and hence disrupted by it, and by the relatively large needle or capillary 
tube used for purpose of puncture injections. Injections of these mesen- 
