226 DISEASES OF CATTLE. 



lowed by metritis, but they are rarely connected with parturition 

 fever. 



All these factors coincide in intensifying the one condition of 

 plethora and point to that as a most essential cause of the 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 

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

 the blood and blood vessels 'is incompatible with the normal func- 

 tional activity of the nerve centers. 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 

 be only a given amount of blood; therefore, if one portion of the 

 brain is congested, 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 

 (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 com- 

 plete recovery from the disease. This does not exclude the other 

 causes above named, nor the influence of a reflex nervous derange- 

 ment proceeding from the udder to the brain. 



SymptoTris. — 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 

 powder ; in one, however, there is such prominent evidence of conges- 

 tion 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 



