Loek-jaw 293 
Tetanus, or “lock-jaw,” is caused by a germ or bac- 
terium that usually enters the system through a wound. 
Once inside, the germs multiply rapidly, and produce 
violent poison that acts upon the nervous system, 
causing the voluntary muscles to contract and, at the 
same time, ereating nervous excitement. The germs 
are believed to be numerous in the soil about barns 
and stables. They are especially liable to enter wounds 
of the feet, although any surgical operation or the 
least break of the skin offers an opportunity for 
infection. When tetanus occurs without any visible 
wound, the germs are believed to enter the system 
through minute wounds, or through a mucous mem- 
brane, such as the digestive tract. 
Tetanus generally centers in some set of muscles, 
such as those of the neck, head, jaws, or back, although 
all the museles may be more or less affected. The first 
marked symptom is usually inability to eat, the muscles 
of the jaws being firmly contracted. The horse he- 
comes stiff all over; the head is elevated and the nose 
protrudes; the tail is arched in a peculiar and char- 
acteristic manner. If forced to move, the animal has 
a stiff, paddling gait. Great difficulty is experienced 
in backing the horse. He is easily excited,- especially 
by a slight blow under the jaws. The “haw” is drawn 
across the inner corner of the eye. The animal grinds 
his teeth, The affected muscles are rigid to the touch. 
The flank is usually “tucked up.” The animal gives 
evidence of being seriously ill. 
Put the horse into comfortable and quiet quarters. 
On no account allow inquisitive visitors to see him. The 
