MIXED NODES 
49 
whether they contain blood or not depends only upon the force of the 
lymph stream. It suffices to change the arterial pressure, and conse- 
quently the lymph pressure, in order to convert a gland from lymph to 
haemolymph gland, and vice versa.t 
In the course of this investigation only a few observations were made 
on human nodes ; but as far as these and the examination of nodes from 
bovines, goats, dogs, cats, rabbits and guinea-pigs were concerned, no 
evidences whatever for the existence of combination forms or the con- 
version of one into the other, have been obtained. Because of the 
comparatively small size of the hemal nodes in most of the domestic 
animals injections were made only on the sheep, bovines and in a few 
goats, t 
Some of the lymph nodes which are indistinguishable often from 
hemal nodes save by injection methods, are comparatively large speci- 
mens which have the color of certain hemal nodes at one end and of 
lymph nodes at the other. Although these hemorrhagic or hemal por- 
tions are often irregular in outline and occasionally ill defined in many 
cases, they are nevertheless quite well defined to the unaided eye. In 
some cases this hemorrhagic area is confined to the interior of the larger 
nodes, and is consequently not evident on external examination alone. 
In addition to such specimens, others which represent all shades in color 
from the gray of lymphatic nodes to a chocolate-brown or a magenta-red, 
are not very uncommon. Still others are so deeply pigmented that they 
are black, and at once suggest anthracosis. These dark pigmented nodes 
also may simulate rare hemal nodes in external appearance, and hence 
may likewise suggest the occurrence of an intermediate group of mixed 
nodes. 
Lewis [13] also emphasized the fact that intermediate forms are 
very numerous, and strangely enough referred to glands in ungulates 
"Many of the largest of which are (9-10 cm.) long and have a cer- 
tain structure recently described by Weidenreich." The latter is then 
said to have described an intermediate form, having blood sinuses only in 
one portion of the node and lymph sinuses only in the rest, each kind 
of sinus occupying a distinct portion of the node. Although emphasiz- 
ing the fact that there are ordinary lymph glands in which ". . . very 
similar and easily mistaken appearances are presented," Lewis further 
tSee also Retterer, Edouard : Des hematies des mammiferes. Jr. de I'anat. 
et de physiol. Tome XLIII, 1907. 
$Hemal nodes were not found in cats, dogs, rats, rabbits and guinea-pigs 
unless we regard them as identical with supernumerary spleens. 
