_Spectroscopic Studies._—Sera obtained from 20 post-mortem bloods were examined spectroscopically. In eight an absorption band in the red was observed. In some instances such a band was observed in blood obtained shortly after death and before coagulation had occurred, while other similar bloods, as well as bloods obtained at longer intervals after death, exhibited no such band. A similar band was observed in one case from blood obtained from a patient about 12 hours before death from pneumonia following influenza. Medication was not a causative factor. To ammonium sulphide the band in the red reacted as methemoglobin and the position (as estimated by Dr. Menten) corresponded with methemoglobin. Oxyhemoglobin bands in such bloods occupied normal positions as determined by Dr. Menten. On diluting such bloods with water no abnormality in character or position bands was observed, save in one instance (No. 778 below). This does not, however, disprove the possibility of such abnormality in the hemoglobin within the cells, for moderate dilution only of serum rendered the band in the red invisible, presumably by dilution. Detailed examination of the absorption bands was made with a direct reading wave-length Hilger Spectroscope (which was calibrated by line spectra derived from salts added to an alcohol flame) by Dr. Menten. This spectroscope had an accuracy of about two Angstroms. In all, seven post-mortem bloods were examined, viz. autopsy numbers 756, 761, 763, 773, 778, 784, and 787. In five of these, sufficient serum was obtained to make readings. All gave the two characteristic oxyhemoglobin bands in the blue-green with centers of the bands at λ 758μμ λ and 542μμ. The second oxyhemoglobin band varied slightly in width in the different samples. In addition to the two oxyhemoglobin bands in each of four of the above sera, viz: Nos. 756, 763, 767 and 787, an absorption band in the red was found with the center of the band as follows: Number 756 at λ 627μμ, number 761 at λ 634μμ, number 763 at λ 625μμ, and number 787 at λ 634μμ. These bands varied considerably in intensity and could only be identified when the two oxyhemoglobin bands were merged and appeared as one broad band. As controls for the position of the oxyhemoglobin bands two normal bands were examined, which showed two bands with centers also at λ 758μμ and λ 543μμ. For comparison of the methemoglobin bands of the above post-mortem bloods, a sample of this hemoglobin compound was made by adding potassium ferricyanide to normal blood until the solution became brownish in color. The center of this methemoglobin band was found at λ 634μμ. In blood from autopsies number 773 and number 778 sufficient serum could not be obtained to make a reading. To each of these bloods distilled water was added. The laked blood of 778 gave a methemoglobin band with the center at λ 632μμ on examination 24 hours after autopsy.