The latest developments of treatment indicate very clearly that the main cause is the production of poisonous, metabolic products (leucomains and toxins) by secreting cells of the follicles of the udder, acting on the susceptible nerve centers of the plethoric, calving cow. Less fatal examples of udder poisons are found in the first milk (colostrum), which is distinctly irritant and purgative, and in the toxic qualities of the first milk drawn from an animal which has been subjected to violent overexertion or excitement. Still more conclusive as to the production of such poisons is the fact that the full distention of the milk ducts and follicles, and the consequent driving of the blood out of the udder and arrest of the formation of depraved products, determines a speedy and complete recovery from the disease. This does not exclude the other causes above named, nor the influence of a reflex nervous derangement proceeding from the udder to the brain. _Symptoms._--It may be said that there are two extreme types of this disease, with intervening grades. In both forms there is the characteristic plethora and more or less sudden loss of voluntary movement and sensation, indicating a sudden collapse of nervous power; in one, however, there is such prominent evidence of congestion of head and brain that it may be called the congestive form par excellence, without thereby intimating that the torpid form is independent of congestion. In the congestive form there is sudden dullness, languor, hanging back in the stall, or drooping the head, uneasy movements of the hind limbs or tail; if the cow is moved, she steps unsteadily, or even staggers; she no longer notices her calf or her feed; the eyes appear red and their pupils dilated; the weakness increases and the cow lies down or falls and after that is unable to rise. At this time the pulse is usually full, bounding, and the temperature raised, though not invariably so, the head, horns, and ears being especially hot and the veins of the head full, while the visible mucous membranes of nose and eyes are deeply congested.