_Causes._ The causes of petechial fever are not clearly made out. Bacteria are found in the early exudate, but these are not constant in kind and it is not unreasonable to suspect that these may be results rather than causes of the lesions. On the other hand there may be an as yet undiscovered organism present, the products of which are capable of producing the disorder. Or the latter may be due to a combination of the toxins of two or more. Among the bacteria found may be named: The pus microbes, cocci, streptococci, staphylococci, and bacilli, have been found and adduced as causes, also diplococci, the bacillus hæmorrhagicus of Kolb, the streptococcus of strangles, the microörganism of contagious pneumonia and that of influenza, with a variety of others too great and too inconstant to be accepted as proof of cause. The fact that rarely more than one animal suffers in the same stable at the same time might be held to oppose the idea of contagion and of a definite organized germ. Hence the theory of its causation by the presence in the system of the toxic products of bacteria rather than the bacteria themselves. (Dieckerhoff.) Cadeac supposes that any toxin which causes capillary dilatation may determine the disease, and calls attention to the fact that the injection of mallein (a vaso-dilator) aggravates the phenomena of petechial fever and determines enormous local exudations and engorgements. He notes further the potent vaso-dilator action of the products of strangles, contagious pneumonia, and influenza which are among the most frequent antecedents of petechial fever. Dieckerhoff also looks on the phenomena as the result of poisoning by the absorbed toxins of the microbes of suppuration, which modify the nutritive changes in the walls of the capillaries and determine exudations and hæmorrhages. Zschokke thinks that there is infection of the intima of the capillaries, with the formation of coagula. Clots are not found, however, apart from hæmorrhages. The toxin theory receives indirect support from the absence of the same specific lesions in simple mechanical congestion of the capillaries and veins. Ranvier had no such results from tying the veins of a rabbit’s ear. Roger tied the auricular veins of the rabbit, and then cut the sensory nerves without effect: he then destroyed the cervical sympathetic ganglion, when there supervened marked exudation, lasting for three days. The complete blocking of veins by pressure or aseptic ligature, does not produce a spreading œdema, whereas in ordinary suppurative phlebitis, with abundance of toxins in the tissues this is a constant result.