_Microbian Infection or Intoxication._ The doctrine has been advanced that the disease is either a microbian infection of the nerve centres or a process of poisoning by the absorbed toxins of microbes. Of the two hypothesis the latter is the more acceptable, in view of the fact, that cows in a condition of coma will sometimes recover with extraordinary rapidity. This is more likely to occur in connection with the elimination or exhaustion of a transient narcotic poison, than with a deadly microbe colonized in the brain. This hypothesis is in full accord with the acknowledged success of the iodide injections; with the observation of Bissauge, which I can endorse, that certain villages and hamlets habitually furnish cases of parturition fever, while neighboring ones, with the same breeds and apparently the same management escape; and with the observations of Russell and Wortley Axe, that the malady will sometimes be suddenly prevented in a herd, by the simple expedient of having the cows moved to a new and previously unoccupied stable, for calving and the first nine days thereafter. In support of the doctrine of a microbian origin is recalled the fact that the disease almost invariably follows parturition, which opened the way for the introduction of bacteria by the genital passages. This is somewhat invalidated by the fact that it follows the easy parturition, in which there was no chance for the introduction of germs on hands or instruments, and does not follow dystokia in which, without question, germs have been planted abundantly in the interior of the womb. Undue weight should not be given to this objection, as the essential accessory conditions of plethora, etc., are usually largely modified in cases of dystokia. The _microbiology_ of the affection leaves much to be desired. Coureur and Pottiez and later Van de Velde found a streptococcus in the blood. Trinchera, Nocard, and Cozette found the common pus cocci (staphylococcus pyogenes aureus, citreus and albus) a streptococcus and a colon bacillus in the liquid squeezed from the cotyledons, and in the liquid debris on the uterine mucosa. These microbes were not found in other organs. They grew readily in artificial cultures, but we lack the final proof of a successful inoculation on a susceptible parturient subject. The whole subject is therefore still a plausible theory.