The mechanism of petechial hemorrhage formation.

ByJ. G. HUMBLE, M.R.C.S., L.R.C.P. T HE OCCURRENCE of petechial hemorrhages in the skin and mucous membranes is a well known sign in many hemorrhagic diseases and in other complaints. Little is known, however, of the mechanism by which they are produced or the exact segment of the vessel or vessels at fault. Histologic preparations show merely an exudation of red cells, sometimes of polymorphonuclear neutrophil leukocytes around the minute vessels in the dermis, the vessel walls themselves usually appearing intact. In the present investigations the formation of petechiae by the tourniquet test (capillary resistance test) in the skin of patients Suffering from various hemorrhagic diseases has been studied by capillary microscopy.