The Bulletin 
23 
posture, the back is bowed, the neck outstretched and the head lowered. 
Within a few seconds, the quivering spreads from the limbs over the 
entire body, increases in intensity, and becomes a violent, involitional 
tremor (Fig. B). This is accompanied by slight, intermittent, tetanic 
contractions of the musculature of the limbs. At this stage of trembling 
ataxia is very pronounced, and the animal is unable to stand (Fig. C). 
It drops quickly into the normal resting posture (Fig D) or assumes 
a characteristic position, in which the head and neck are outstretched 
and the jaw is resting upon the ground (Fig. E), whereupon the trem¬ 
bling apparently immediately ceases. If the sheep is made to rise 
after it has lain down for a few moments, a second and more violent 
spasm of trembling ensues with a repetition of the symptoms as de¬ 
scribed. Trembling may recur repeatedly every time the animal is 
made to rise. The quiescent period is shortened, however, after each 
spasm of trembling and may begin as soon as the animal is placed on 
its feet. Even after the disease has progressed to the point where trem¬ 
bling is violent, many animals still possess considerable appetite. 
After the second or third day, the animal becomes comatose and may 
lie prostrate on its side (Fig. F) until death occurs. There is gener¬ 
ally a very considerable decrease in weight, most of which occurs during 
the two or three days preceding death. The feces generally remain 
normal, with, in some cases, a small amount of mucus. Urination is 
more frequent than in healthy animals and only a small quantity is 
voided each time. Vomiting occurred in the case of two animals under 
observation, and a frothy discharge from the nostrils is not uncommon 
after coma sets in. 
c. In Hogs .—The symptoms of trembles as observed in hogs are in 
general like those in sheep. There is first a listlessness, not accompanied, 
however, by any marked loss of appetite. The animal remains lying 
unless urged to rise, or unless food is offered, whereupon it stands with 
hind feet placed well under the body. In this position, the head droops, 
the eyes are partially closed, and the hack is bowed. (Fig. I.) There 
is no lack of coordination of movement in walking for the first few 
days, although the hind legs are markedly stiff. Later, this stiffness 
appears in the fore limbs. After the pig has stood for a few minutes 
while eating at the trough or is driven around in the pen a slight 
quivering in the legs begins. Within a few moments, the trembling has 
become progressively more severe, has spread over the entire body and 
becomes a violent shaking or tremor, so acute that the animal squeals, 
presumably with pain, in its efforts to remain on its feet. At this 
stage of trembling the animal either falls to its knees or sits upon its 
haunches (Fig. J). From this position, after a moment, it falls into 
