The symptoms of the development of insolation occur very rapidly. In animals of the bovine species there is accelerated respiration, which soon amounts to dyspnœa. The mucous membranes then become cyanotic. The animals attacked seem anxious, although not agitated, and soon afterwards the eyes water, the mucous membrane and the lips of the vulva display œdematus infiltration and congestion, and areas of cutaneous congestion, closely resembling mud fever in the horse, appear over the mammæ. At this stage the animals move with difficulty, and show all the symptoms seen at the outset of gangrenous coryza.
All these symptoms develop in one, two, or three hours, and death may follow if nothing is done. They disappear, however, as rapidly as they appear. In an hour or less we have seen in some cases a complete return to the normal condition. Given the facts, the diagnosis is extremely easy.
Treatment. Treatment should be commenced by immediately removing the animal to a cool, airy, shady place. It may then be bled, and the head and neck should be freely drenched with cold water. The symptoms generally disappear as though by magic.
POST-PARTUM PARALYSIS—MILK FEVER—MAMMARY TOXÆMIA—PARTURIENT APOPLEXY—DROPPING AFTER CALVING.
For a great part of the following short account we are indebted to an excellent report by J. J. Repp, V.M.D., in the Journal of Comp. Medicine and Veterinary Archives, September, 1901:—
The word “fever” in connection with the terminology of this disease is not very appropriate, because in the majority of cases fever is not present, but the animal has a subnormal temperature. The term milk fever is very misleading and indefinite, as it is also used by the laity to designate other diseases, such as parturient septicæmia and the various forms of mammitis. Parturient paralysis must be clearly differentiated from parturient septicæmia, which is a disease of an entirely different character and which may occur in any of the domestic species, whereas parturient paralysis occurs only in the cow.
Distribution. Parturient paralysis occurs wherever milch cows are kept. It is more prevalent in dairy districts, because it is the heavy milking strains of cows that are most subject to the disease.
Cause. No definite cause can be assigned for this disease. Schmidt’s theory is that parturient paralysis is caused by the evolution in the mammary gland of a poisonous substance through the over-activity of the epithelial cells of this gland excited by the determination to the udder after birth of large quantities of blood which was supplied to the uterus and the fœtus before birth, but which now goes to the udder because of the natural demand for milk secretion. This poisonous substance being carried in the circulation to various parts of the body, brings on the symptoms which characterise the disease. It is well recognised that living cells may, under certain circumstances, produce poisonous substances. Schmidt’s theory, therefore, is in accord with an established principle.
Pathogenesis, or generation, of the disease. Parturient paralysis, as a rule, occurs in cows 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 vaso-motor 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 anæmic, œdematous, easily torn, and yellowish in colour. In other cases it shows hyperæmia of the meninges and of the brain substance.