lungs have been expanded, as, for example, during the inspiration of hydrogen. There has been much discussion as to the cause of the cessation of the circulation in asphyxia. It is probably due to the want of that force (" vis e fronte") which is coinci- dent with the changes that take place between the blood and the oxygen.
2. Death by Coma.—Death by coma is occasioned by certain morbid states of the encephalon. These in the first instance cause stupor and loss of consciousness ; subsequently the reflex actions which are concerned in the respiratory function are no longer effected. Impressions conveyed by the branches of the pneumo-gastric and 5th pair of nerves, do not lead to the generation of motor impulses. The action of the diaphragm ceases, and the chest no longer expands, and, as a necessary result, air is just as much excluded as if there had been a mechanical obstacle to its entrance. So far, therefore, as the circulation through the lungs is concerned, there is no difference between death by coma and death by asphyxia. The cavities of the heart will be equally distended with blood in each case. But between these two modes of death there is this difference : in the former loss of consciousness precedes, in the latter follows, the respiratory derangement. On this account death by coma is said to be "death beginning at the head" ; that by asphyxia "death beginning at the lungs" ', that by syncope " death begin- ning at the heart."
Whenever there is disease or injury of the upper part of the spinal cord, death by asphyxia may occur without coma, but such cases are not common. More or less coma usually precedes the fatal termination.
It is of much importance, in the management of many diseases, to know the kind of death that is to be apprehended ; for it will be found, that an essential part of their treatment consists in the adoption of measures which are calculated to maintain and support the function, the failure of which is impending.
