230 DISEASES OF CATTLE. 



plethora. If this is not speedily counterbalanced by a free secretion 

 from the udder, kidneys, bowels, and other excretory organs, the most 

 dire results may ensue. Calving may thus be held to be an exciting 

 cause, and yet the labor and fatigue of the act are not active factors. 

 It is after the easy calving, when there has been little expenditure of 

 muscular or nervous energy, and no loss of blood, that this malady is 

 seen. Difficult parturitions may be followed by metritis, but they are 

 rarely connected with parturition fever. 



All these factors coincide in intensifying the one condition of pleth- 

 ora, and point to that as a most essential cause of this affection. It 

 is needless to enter here into the much-debated question as to the 

 mode in which the plethora brings about the characteristic symptoms 

 and results. As the results show disorder or suspension of the nerv- 

 ous functions mainly, it may suffice to say that this condition of the 

 blood and blood vessels is incompatible with the normal functional 

 activity of the nerve centei-s. How much is due to congestion of the 

 brain and how much to bloodlessness may well be debated, yet in a 

 closed box like the cranium, in which the absolute contents can not 

 be appreciably increased or diminished, it is evident that, apart from 

 dropsical effusion or inflammatory exudation, there can only be a 

 given amount of blood; therefore, if one portion of the brain is con- 

 gested another must be proportionately bloodless, and as congestion 

 of the eyes and head generally, and great heat of the head are most 

 prominent features of the disease, congestion of the brain must be 

 accepted. This, of course, implies a lack of blood in certain other 

 parts or blood vessels. 



The latest developments of treatment indicate very clearly that the 

 main cause is the production of poisonous metabolic products (leuco- 

 mains and toxins) by secreting cells of the follicles of the udder, act- 

 ing on the susceptible nerve centers of the plethoric, calving cow. 

 Less fatal examples of udder poisons are found in the first milk (colos- 

 trum), which is distinctly irritant and purgative, and in the toxic 

 qualities of the first milk drawn from an animal which has been sub- 

 jected 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 prod- 

 ucts, determines a speedy and complete recovery from the disease. 

 This does not exclude the other causes above named, nor the influ- 

 ence of a reflex nervous derangement proceeding from the udder to 

 the brain. 



Symptoins. — There may be said to be two extreme types of this dis- 

 ease, with intervening grades. In both forms there is the characteris- 

 tic plethora and more or less sudden loss of voluntary movement and 

 sensation, indicating a sudden collapse of nervous power; but in one 



