330 The Circulation through the Dog’s Spleen 
9 ce. in 10 minutes. The vein was now closed for 15 minutes and then 
the animal was killed by cutting the aorta. During the time the vein 
was closed the spleen became very much distended with blood. The 
spleen was now cut out, leaving the veins and arteries freely open. Dur- 
ing the 5 minutes which followed the normal end of the spleen con- 
tracted to a solid mass, the paralyzed end contracted slightly and the zone 
between contracted markedly. Careful examination showed that there 
were no clots in any of the veins. Frozen sections, after the spleen had 
been hardened in formalin, showed that the pulp of the paralyzed end 
of the spleen was filled with blood, that of the normal end was free 
from blood, and that in the intermediate zone there was some blood in 
the veins and some in the pulp. Experiments of this sort only show 
that the blood which enters the pulp after the vein is closed is not 
expelled in case the muscle of the spleen is paralyzed 
A better test is made by injecting the nitrite through the artery. 
This can be done easily by inserting the cannula into one of the anasto- 
moses to the stomach, pointing towards the spleen, and when the fluid 
is injected the main artery is to be clamped to prevent the fluid from 
escaping into the aorta. Of course all of the anastomoses are to be 
tied. If aspleen is injected in this way for ten minutes it is found that 
the muscle is paralyzed completely. Then by closing the cannula and 
opening the main artery the normal circulation is re-established. In 
ease the first blood enters the pulp directly it should be found filled 
with red blood corpuscles. So at the end of one minute the spleen was 
cut out with one stroke of the scissors, leaving the main arteries and 
veins open. The paralyzed end of the spleen did not contract. The 
specimens were placed in strong formalin at once and frozen sections 
were. made a few days later. They showed that the pulp was gorged 
with blood in the paralyzed portion of the spleen. It was practically 
impossible to find the line of demarcation between the pulp and the 
veins. As the end of the spleen which was not paralyzed was ap- 
proached the pulp was found to contain a much smaller number of red 
blood corpuscles, but at no point was it full of them. Experiments of this 
kind show that when the muscle of the spleen is paralyzed with sodium 
nitrite the blood which enters the artery passes first into the pulp- 
spaces and remains there, for there is no muscular contraction to expel it. 
Probably the most satisfactory experiment is made by paralyzing the 
muscle of the spleen so quickly that it has no time to contract and empty 
the pulp-spaces. This can be accomplished by making an interstitial 
injection with strong formalin and. then removing the spleen at once and 
with one stroke of the scissors. The whole experiment can be performed 
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