After having injected intraperitoneally, such substances as extracts of the bone-marrow, liver, spleen as well as skeletal muscle, once a day, and in determining quantitatively, the nucleic acid contained in rabbit's bone marrow, liver, spleen, and kidney, in pursuit of the lapse of time, from 6 hours to 9 days, obtained results as follows: 1) The amount of organ nucleic acid (mg/100g) for a healthy rabbit proved: bonemarrow: DNA 728, RNA 45.7. liver: DNA 36.6, RNA 88.9. spleen: DNA 100.2, RNA 65.3. kidney. DNA 38.4, RNA 56.3. 2) By injection of bone marrow extract, the bone marrow DNA, after having decreased for a time, increased; so did RNA too. The liver DNA showed an increase, while, RNA decreased. The spleen DNA increased, after having decreased; RNA, ambiguous. Kidney nucleic acid proved variable, but in general showed increase in DNA. 3) By injection of liver extract, the bone-marrow nucleic acid proves increase in both the constituents, through a temporal decrease; while, RNA increases, The nucleic acid amount in the liver is indefinite but in general, proves certain decrease; kidney nucleic acid, whereas it is lacking in general in DNA, having once abated, newly increases. 4) In injection of liver extract, in general, bone marrow-DNA proves increase, while RNA increases after a decrease. In the liver, DNA shows an increase after a little time of decrease, while, RNA seen to have kept increasing in all. In the spleen, both DNA and RNA have a tencency to increase after having shown a slight decrease. As to kidney, there was observed a marked decrcase of RNA. 5) In case skeletal muscle extract has been injected, bone marrow RNA indicates more remarkable increase than with other extracts; in the liver both nucleic acids, esp. RNA increases; as to spleen, there RNA has generally been fixed; but DNA proves decrease in proprotion to the frequency of injection; while, the kidney nucleic acid show little change.