d) Irradiation of the body of normal animals killed by decapitation, under ether anaesthesia, produces small amounts of conjugated fatty acids. In early experiments, different organs obtained from slaughterhouses were irradiated and fatty acids examined. In general, even after intensive radiation, corresponding to 4,000 r. in one treatment, the oxalic index of fatty acids was never found to be above 1, corresponding to 1 mg. of oxalic aciJ obtained from one gram of fatty acids.

Fig. 82. Curve of spectral analysis of the cod liver oil fatty acids after chemical conjugation, shows the presence of di-, tri-, tetra-, penta-, and hexaenic members.

e) On the other hand, the amount of conjugated fatty acids in the bodies of living animals receiving radiation increases significantly. The following experiment is illustrative. Eighty rats of the same sex, age and weight (about 180 gms.), separated into several groups, were given 1500r.. delivered by a therapy unit with no filter. Four control animals were killed before exposure. Groups of four treated animals were sacrificed periodically, starting immediately after irradiation, at 2, 6 and 24 hours after irradiation, and each day thereafter until all animals died or had been killed.

Fig. 83. Absorption spectra (0.002% in ethyl alcohol/ethyl alcohol) in ultraviolet of commercially available linoleic acid (with small amount of linolenic acid) non irradiated (----) and irradiated with beta particles from 25 mg monel metal filtered radium/10 cc at 37°C for four hours. Some conjugation occurs in the control when kept in the incubator.

During this time, nontreated control animals, kept under the same conditions, were also sacrificed. The quantity of conjugated fatty acids even in animals which showed no visible ill effects at the time they were killed.

Fig. 84. Absorption spectrum of the same material as in Fig. 83, non irradiated (....) and irradiated with alpha particles from 150 mc Thorium X/10 cc at room temperature for 7 days. (-) found in the entire body of each individual animal at the time of death was determined by means of the oxalic acid index method.

The oxalic acid index for fatty acids in the bodies of untreated control animals was usually zero. Occasionally there was a variation from 0 but it was always below 0.6. Irradiated animals killed within the first two days showed an irregular increase in conjugated fatty acids, with oxalic acid index values of between 0.6 and 5.1. Three days after irradiation, the oxalic index was above 3 in all the dead or sacrificed animals. The index rose even in animals which showed no visible ill effects at the time they were killed.

Fig. 85. Fatty acid conjugation induced by irradiation in vivo. Changes in the oxalic index of total fatty acids of rats irradiated with a lethal dose (1500r). Sacrificed at different intervals, the oxalic index of their fatty acid shows progressively increasing values. The animals die when the index has arrived at a critical value between 14 and 17.

The index increased continuously with the passage of time until the animals died. By the fifth day, it was above 6 for all animals and, by the seventh day, with few exceptions, it was around 10. After the twelfth day, it had risen above 12 in most of the animals. In all animals which were sacrificed after the 13th day or which had died at any time, the index showed values between 14 and 17. (Note 2) Figure 85 shows these results in the group of rats described in this experiment. These changes were observed when the same procedure was repeated in other groups of animals. These experiments clearly indicated that the quantity of conjugated fatty acids progressively increases in the days following the exposure in animals treated with one lethal dose of X ray. Death occurred when the amount of conjugated fatty acid reached a critical level equivalent to an oxalic acid index value between 14 and 17. The spectral analysis of fatty acids of animals treated with radiation showed changes corresponding to the presence of conjugated isomers. These appear in the samples of fatty acids obtained from the entire body of these animals. (Figs. 86 and 87) Still more evident were the conjugated trienes in the fatty acids of organs. Figures 88, 89 and 90 show the difference in such analyses as compared to corresponding untreated controls. The presence of conjugated trienes appears clearly in the characteristic peaks.

Fig. 86. Spectral analysis (.01 in ethyl alcohol) of the total fatty acids obtained from the body of rats irradiated with 1500r shows changes more manifest around 270 mµ. The oxalic index of the preparation is indicated and shows a parallel increase with the changes in the curve.

Fig. 87. Spectral analysis (.01 in ethyl alcohol) of the fatty acids of the total body of a mouse irradiated with 1500r, shows an increase in fatty acids with the absorption corresponding to 270 mµ, as compared with the control.

The concept of a critical value for the oxalic index is supported by other studies in which the same value is found in animals dying after adrenalectomy or after thermal, chemical or traumatic states of shock. Even in animals dying in superacute shock, within 3 to 5 minutes after being severely scalded in hot water, the level of conjugated fatty acids is higher than in controls.

Fig. 88. Spectral analyses (.01 in ethyl alcohol) of the fatty acids of the kidney of a normal rat and of a rat irradiated 6 days previously with 1500r. The peaks characteristic for conjugated trienes are seen.

When the irradiated dose was not a lethal one, that is, below 600 r. in our experiments, the oxalic index increased at first but decreased after about two to three weeks. It never reached the critical value of 14-17. (Fig. 91, Note 3)