By means of various staining methods, the author investigated the pathohistological changes in the suprarenal gland of guinea-pigs, suffering from acute diffuse peritonitis through the injection of bac. coli in abdominal cavity, and compared these alterations with other accompanying changes. The results may be pointed out as follows: 1) Structure of the suprarenal gland of guinea-pigs, which were suffering from acute diffuse peritonitis, shows definite pathohistological alterations accompanied by the change of ascorbic acid content at the same time. 2) Histological changes occur most profoudly at the 13th hour. Ascorbic acid content also diminished greatly by this time. 3) Prevalent alterations observable under haematoxylin-eosin staining are swelling, turbidity, vacuole formation and necrosis of cell, hyperchromatic staining of nucleus, karyoklasis and karyolysis, vasodilatation, hyperaemia, blood stagnation and haemorrhagia. These alterations are due to the direct action of bacteria or to its toxin. 4) The above described histological alterations as well as the change of ascorbic acid content are rather diminished in degree at the 24th hour than at the 13th hour. This facts indicate that the pathological process has been stopped or becomes healing by this time. 5) Neutral fat increases slightly at the 6th hour, highly at the 24th hour. 6) Increase or decrease of lipoid content., tested by Ciaccio's method, are inconsistent compared with those of neutral fat. 7) Double refractive substances and silver granules diminished at the 24th hour even in control animals, but these diminution is profound in all cases of suffering ones after the 6th hour. Though the former substance could not be detected in medulla, the latter are richly distributed in it. 8) The histological alterations in medulla are very feeble, compared with those in cortex, and lipoid substances are not detectable in the former. 9) If there are increases of the weight of suprarenal gland in case of purulent peritonitis, we could always confirm the presence of oedema, hyperaemia and blood stagnation of high grade in the gland.