28 HAY AND FODDER. 
practically abandoned, in favour of a chemical basis. 
Aconitic acid was first found and suspected. Later work 
disclosed an alkaloidal nerve poison, called equisetin, 
which was proved to be present in one species at least, in 
sufficient quantity to be dangerous to animals. Whatever 
the nature of the poison, numerous instances of its harm- 
ful effect have’ been recorded. It is especially injurious 
to horses. In one much quoted case, nine horses, fed on 
good hay, were bedded with swale hay containing the 
Horsetail. They acquired the habit of eating their bed- 
ding and as a result all soon showed symptoms of Equi- 
setosis. The youngest, three years old, became unable to 
stand, and died in a few days. Others, somewhat older, 
became very ill, keeping on their feet with difficulty, 
but finally recovered. One mare, much older than the 
rest, showed only slight symptoms. Five other horses on 
the same farm, fed in the same way, but bedded with 
straw, remained in perfect health. 
In this country the Field Horsetail, Equisetum arvense 
L., causes most trouble because it is often found in hay, 
especialiy from low lying fields. Animals may graze in 
pastures containing Horsetail without harm, either be- 
cause of the laxative effect of the green forage or because 
they can pick their food better than when fed in the stall. 
Grain-fed work horses seem little liable to attack, while 
colts or young animals are chiefly affected. Cattle eat the 
Field Horsetail without apparent harm, although other 
species in Europe are said to be poisonous to them. The 
effect of Horsetail on sheep is doubtful. 
A noteworthy indication of incipient Horsetail poison- 
ing is the development of a depraved appetite, the animal 
often eating its bedding with Horsetail.in it 
in preference to good hay or even grain. After 
the disease develops the symptoms are quite as marked. 
Symptoms 
