Gas is frequently formed in the tissues after death, but there are some cases in which the development of gas, especially in the liver, is so marked and extensive that special attention has been attracted to them. In the cases referred to the liver is found more or less honey-combed with cavities, produced in the substance of the organ by an evolution of gas in many centres. A similar evolution of gas occurs in the kidneys, spleen, in the subcutaneous tissues, where it produces emphysema, and elsewhere. A peculiar odour is exhaled by the affected organs. In such cases the organs have been found the seat of colonies of microbes, which comprise several species. One variety commonly found is a short bacillus with rounded ends which stains with the ordinary reagents and also with Gram's method. It is present in the walls of the gas cavities but also in the blood-vessels, being found in the case of the liver in portal and hepatic branches and capillaries. The microbe may be cultivated in the ordinary media, and it is anaerobic. It produces gas abundantly in the cultures.

It is certain that the principal growth of this microbe is postmortem, but its wide dispersion and abundance in the blood suggest that it may have been planted during life. Most of the cases in which the condition has been observed are septic, that is to say, there are external wounds. But there are cases, of which the author is cognizant of at least two, in which a rapidly fatal illness having the characters of toxaemia (so-called blood-poisoning), but without any external wound, have been associated with the condition under consideration, and with no other apparent cause for the symptoms. Similar cases have been recorded by other observers.