The free consumption of ice cold water by the healthy dam causes active gastro-intestinal peristalsis and vigorous movements of the advanced fœtus, which can be seen or felt in the right flank, so that this is often resorted to, to determine whether the animal is pregnant or not. If this is frequently repeated or carried to excess in susceptible animals it will at times cause abortions. As in all other cases of mechanical or physiological disturbance, this is most operative at those periods of constitutional changes, which if the animal had been unimpregnated would have brought about ovulation and œstrum.
The greedy ingestion of cold aliments, like frozen roots, or green vegetation covered with hoar frost, may have a similar action, the more so that such aliments are extremely fermentescible and liable to cause tympany and undue pressure on the gravid womb.
Even without ingestion, exposure to cold rain or snow storms or the plunging in ice cold water tends to produce excessive peristalsis and fœtal movements and thereby prove injurious.
Mechanical injuries to the abdomen as crushing by a gate, kicks, hooking with horns or tusks, hounding with dogs, riding of each other when a cow is in heat, are liable to produce congestions, detachment of fœtal membranes, and even death of the fœtus.
Very fermentescible foods like those following a wet season or bad harvest, or those made of the leafy albuminous plants like lucerne (alfalfa), sainfoin and clover, act injuriously in the way of causing tympanies and compressions, but it must also be recognized that we are here dealing with fodders abounding in bacterial ferments, and that some of their products may act physiologically as ecbolics, even if the bacteria themselves do not colonize the genital passages as infections.
Insufficient food or very innutritious forage, too close stabling, heavy milking, early breeding (dam or sire), inbreeding, are liable to lower the general stamina and throw the system more open to the action of other factors.
Stagnant, corrupt drinking water has been charged with causing abortion, and the trouble has ceased when it has been withdrawn, but it is difficult to estimate its value in different cases—disturbing digestion, fermentation, poisoning, or introducing of actual infection.
Ergoted grasses and smut in maize, wheat or oats, have been often charged with wide spread abortions, and though each has in turn been administered in large and continuous doses without causing abortion, this does not invalidate the many cases in which it manifestly had that effect, nor does it show that obstetricians have been mistaken in their almost immemorial trust in ergot as an ecbolic. It must be recognized, however, that grown under different conditions, of sunshine and shade, and harvested at different stages of its development, ergot varies greatly in its physiological action, as it does also from having been overkept and thus one specimen is effective or dangerous while another is absolutely ineffective. The specific action of the alkaloids in determining contraction of involuntary muscular fibre, is seen alike when used medicinally and when acting as an accidental toxic agent in causing spasms, nervous torpor or paralysis, delirium; gangrene of the feet, tail or tip of the ear; or contraction of the womb and expulsion of its contents. Like other agents mentioned ergot is at times an active ecbolic when coöperating with other similarly operating agencies.
Irritant vegetables of various kinds are to be dreaded. Such as act on the bowels and kidneys, keeping up a constant diarrhœa and diuresis, are quite liable to cause abortion in susceptible subjects. Savin, tansy and rue have obtained a bad reputation in this sense.
Cotton root bark is an active ecbolic, but is not likely to harm animals unless deliberately administered.