20 
HEMOLYMPH NODES OF THE SHEEP 
independent of the lymphatic system, injections were also made from the 
abdominal vena cava and aorta, in order to determine whether the spaces 
found in hemal nodes are in direct connection with these vessels. Such 
injections were made on two lambs seven to eight months and four to 
six weeks old, and six foetuses from four to five months old. Three of 
these lambs were bled to death. In case of the other lamb and the 
foetuses, some relief from back pressure due to the contained blood was 
secured by incision of the vena cava. Injections of filtered carmine and 
Prussian blue gelatine were made directly into the abdominal portions 
of these vessels. The carcasses were kept immersed in warm water and 
a high uniform pressure (200-250 mm. Hg.) was maintained continuous- 
ly for a period of one-half to three-fourths of an hour. Besides this, 
the injection was limited as far as possible to the lumbar region by 
clamping the main branches of the great vessels. Since the injection 
mass was thus limited to a small field, the behavior of the hemal and 
lymphatic nodes could be observed more carefully during the progress 
of the injection. Although at first it was attempted to mark the site of 
some of the typical hemal nodes, by transfixing the adjacent tissue with 
a small pin, the high pressure used on the filtered gelatine caused con- 
siderable leakage at the point of puncture, which threatened to obscure 
the field. Hence this method was abandoned. 
Upon completion of the injections, the bodies of the foetuses were 
cooled, and fixed, in toto, in formaline. In case of the lambs, the whole 
lower half of the body was likewise preserved, in order to leave the area 
under observation undisturbed. All nodes were later dissected out by 
means of a lens when necessary, and cut serially in paraffine. It was 
found advisable to remove all nodes found in a given area, because of 
the difficulty, or impossibility even, of distinguishing injected hemal and 
lymphatic nodes by external appearances. 
During the course of the injection it was disappointing to notice 
how quickly even the smallest lymph nodes, distant often from the place 
of injection, would quickly change their color due to entrance of the 
injection mass, while much larger near-by typical — as judged by external 
appearances — hemal nodes showed no color change whatever. That this 
apparent failure to inject the great majority of the hemal nodes was not 
due to a faulty technique, was shown by the fact that the whole carcasses 
were so well injected, in spite of ligation of the main branches of the 
great vessels, that even the small parathymus glands had changed their 
color and were found on microscopic examination to contain much injec- 
tion mass. 
