462 ' NERVOUS SYSTEM. 



living cells may, under certain circumstances, produce poisonous sub- 

 stances. Schmidt's theory, therefore, is in accord with an established 

 princij^le. 



Pathogenesis, or generation, of the disease. Parturient paralysis, 

 as a rule, occurs in co^YS which give a heavy flow of milk and which 

 are in a high state of nutrition. It may develop at any age, but is 

 extremely rare in cows before they have reached adult age and have 

 given birth to several calves. It is also rare in old cows. It occurs, 

 then, in cows which are of middle age and in the full height of their 

 activity as milk producers. The disease attacks the cow after she has 

 given birth to a calf, usually within twenty-four hours thereafter, but in 

 some cases not until a week or even a month after parturition. In a few 

 cases the disease has its inception a short time before parturition. Cows 

 which are stabled and deprived of exercise are said to be more prone to 

 the disease than those which are permitted to exercise at will. There 

 are many exceptions to this statement, although it is the usual teaching. 

 Further observation may show that it is not correct. In Iowa more 

 cows take this disease while at pasture than in any other circumstance. 

 This doubtless arises from the fact that in Iowa cows are given more 

 freedom than is customary in older dairy States. The disease may arise 

 at any time in the year, but, on account of the fact that spring-time is 

 pre-eminently the calving season, most cases originate at this season. 



Morbid anatomy. The morbid alterations are limited and variable, 

 and offer nothing characteristic. The blood is irregularly distributed, 

 a condition which probably indicates marked vasomotor disturbance 

 resulting from the profound interference with the nervous functions 

 which accompanies the disease. The abdominal organs are usually 

 filled with blood. The brain may be anaemic, (Edematous, easily torn, 

 and yellowish in colour. In other cases it shows hypenemia of the 

 meninges and of the brain substance. 



Symptoms. The disease usually appears within twenty-four to forty- 

 eight hours after parturition. In extreme cases it may not occur until 

 two months or even six months after parturition. It may rarely occur 

 before birth. It usually follows an easy birth. At the onset of the 

 disease the cow manifests some uneasiness ; it moves about in a rest- 

 less manner, stamps, strikes the abdomen with its hind legs, perhaps 

 bellows, grinds the teeth, and may have spasms of groups of muscles 

 or even a general convulsion. After this period, which may be un- 

 noticed, the symptoms of paralysis come on. The cow shows weakness, 

 staggers, and at last falls. As the paralysis advances it stretches on 

 the ground, lying on its side usually with the, neck bent to one side so 

 as to bring the nose into the flank or the costal region. This is the 

 characteristic position in parturient paralysis. If the head is brought 



