DISEASES FOLLOWING PARTURITION. 223 



colds of winter are no protection against it. Heat, however, conduces 

 to fever, and fever means lessened secretion, which means a plethoric 

 state of the circulation. The heats of summer are, however, often 

 only a coincidence of the real cause, the mature rich pastures, and 

 especially the clover ones, being the greater. 



Electrical disturbances have an influence of a similar kind, disturb- 

 ing the functions of the body and favoring sudden variations in the 

 circulation. A succession of cases of the malady often accompany or 

 precede a change of weather from dry to wet, from a low to a high 

 barometric pressure. 



Costiveness, which is the usual concomitant of fever, may in a case 

 of this kind become an accessory cause, the retention in the blood of 

 what should have passed off by the bowels tending to increase the 

 fullness of the blood vessels and the density of the blood. 



Mature age is a very strong accessory cause. The disease never 

 occurs with the first parturition, and rarely with the second. It 

 appears with the third, fourth, fifth, or sixth — after the growth of the 

 cow has ceased and when all her powers are devoted to the produc- 

 tion of milk. 



Calving is an essential condition, as the disturbance of the circula- 

 tion consequent on the contraction of the womb and the expulsion 

 into the general circulation of the enormous mass of blood hitherto 

 circulating in the walls of the womb fills to repletion the vessels of 

 the rest of the body and very greatly intensifies the already existing 

 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 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 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 



