C. =Constitutional Causes.=--Among these are to be mentioned particularly that symptom-complex ordinarily known as _diabetes_ or _glycosuria_. This means a depraved condition of the system in which gangrene is threatened or permitted under circumstances which otherwise would have little or no disastrous effect. Thus _diabetic gangrene_ has come to be one of the recognized manifestations of the general disease. That the trophic nerves have a more or less pronounced effect in determining gangrene in certain cases seems to be now quite well established. It is well known how quickly _bed-sores_ form after injuries to the spine, while in certain nervous affections a minimum of friction of the skin may determine its death, particularly about the labia or scrotum. It is said that the insane, when made to sleep by chloral, may develop decubitus from pressure in a single night. There is also a well-known form of _symmetrical gangrene_, known sometimes as _Raynaud’s disease_, which is characterized by symmetry of lesions and absence of definite pathological changes (Figs. 14 and 15). The so-called _digiti mortui_, or _dead fingers_, and _erythromelalgia_ are examples of this character. A condition almost leading up to gangrene, but perhaps not absolutely terminating in such a way, has been known as _local asphyxia_, which seems to be a condition of arterial spasm with venous congestion and slight edema. While the aged will often recover from a legitimate surgical operation without disturbance, it is, nevertheless, true that senile gangrene commencing in the toes has for its cause some very trifling injury or lesion, such, _e. g._, as paring of a corn, or the like. This shows a weakened local and general resistance, as well as the wisdom of redoubling aseptic precautions in operations upon such patients. As constitutional causes also should be included the deleterious effects of certain drugs, particularly ergot, mercury, and phosphorus. D. =Infectious Causes.=--In the instances already mentioned reference to the infectious microörganisms has been avoided. There remain to be considered types of gangrene due to the activity of certain microörganisms--_hospital gangrene_, _phlegmonous erysipelas_, _malignant edema_, _gangrenous emphysema_, _noma_, _ainhum_, etc.