It is well established that the red corpuscles, which are introduced into the blood stream of the other animal, are taken by some special tissues, and the latter finally was immunized. Now, it will be very interesting to see what will become of the red corpuscles, when they are further introduced into the animal, and especially to see the influence of the thyroid gland in this case. In respect to these problems, the following experiments were carried on.
1) The red corpuscles of the fowl was first injected into, the marginal vein of the ear of a normal rabbit. In this case, we found almost no corpuscle in the capillaries of the lung, but a larger number of them in the capillaries and the endothe lial cells of the liver.
2) When we repeated the experiment on the immunized rabbit, we found the red corpuscles more abundantly in the lung and more scantily in the liver than in the first experiment.
3) The third experiment was carried out on a thyroidectomized rabbit, being immunized by two successive injections of the corpuscles. With the third injection most of the experimental animals died with agony, immediately after the operation. The lung showed an aspect of white infarct, while on histological examination the structure of the alveoli was found almost destroyed. Such a change of alveoli involved the detention of many destroyed erythorocytes of the fowl and the infiltration of the leucocytes of the rabbit. In the endothelial cells of the liver the foreign red corpuscles were still found, though very scantily.
4) A rabbit was fed on thyroid substances and was immunized by fowl's red corpuseles. With further injection the corpuscles were taken up in the endothelial cells of the liver, more abundantly than in the case of the thyroidectomized rabbit, but were less than in the normal ones. In the lung a few number of the red corpuscles were found as well as in that of the second experiment.
5) From the results above, it may be concluded that :
The extirpation of thyroid gland decreases the vitality and immune activity. Therefore, when red corpuscles of the fowl were introduced into the body of an operated rabbit, they are retained in the pulmonaly capillaries, and the lung shows an aspect of white infarct. The extirpation causes also a decrease in the activity, especially their power of taking up the foreign substances, of the endothelial cells of the liver. On the other hand, the feeding on thyroid substances favours the general vitality of the organism and increases its immunactivity. The function of the endothelial cells is, therefore, strengthened and no detention of fowl's red corpuscles in the pulmonaly capillaries occurs.
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