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of such areas varying in size from an acre to several thousand acres. 
u Milksick Mountain,” in White County, Tenn., is entirely inclosed 
by a fence 7 or 8 miles in length, built about fifty years ago; since 
which time the disease has been very rare in that locality. 
The infected areas are always wooded land, but otherwise differ 
markedly, from dark damp ravines to high dry ridges or ordinary 
level forest tracts. Seaton (1841), who wrote extensively on the sub- 
ject, claimed that the disease was found only where sandstone en- 
tered largely into the composition of the soil. Other writers do not 
agree with this view. 
There appears to be a very general agreement in the opinion that 
wooded land is essential for the existence of the disease and the 
clearing of the land suffices to remove all danger of animals ac- 
quiring trembles. It is said that if land, once the seat of the disease, 
be rendered harmless by clearing, then be permitted to produce a 
new growth of timber it may again become the seat of the disease. 
So sharply are some milk-sick areas defined that farmers point out 
places where on one side of a fence animals may be pastured in per- 
fect safety, whereas if pastured on the other side of the fence they 
are almost sure to contract trembles. I have been told of more than 
one outbreak of trembles due to changing the fence of a pasture by 
a few yards so as to include some wild (uncleared) land. 
It has been claimed that springs and water courses have conveyed 
the cause of trembles, but it seems clear that in such cases the animals 
contract the disease in the surrounding wooded areas. 
Etiology and pathology . — Children appear to be less liable to the 
disease than adults. Nursing women are said to enjoy a relative im- 
munity (Johnson, 1866). One attack confers no immunity; in fact, 
it appears to predispose to subsequent attacks (Philips, 1877). 
The disease occurs most frequently in the spring and the fall, but 
records of cases in summer are not rare and a few are said to have oc- 
curred in winter. Drake (1811), who investigated the subject in 
Ohio, states that the disease occurred in May and June, but was more 
frequently met with in August, September, October, and November. 
The majority of writers agree with this, stating that cases are most 
frequent in the fall months, and especially when the season has been 
clrv. The last outbreak in Tennessee occurred in April, and the gen- 
eral impression prevails among physicians and laymen in that State 
that the disease occurs only in the spring and the autumn. 
So far as milk sickness in man is concerned about the only etiologi- 
cal fact of importance is that the disease occurs as a result of the use 
of milk, butter, cheese, or flesh from an animal suffering from trem- 
bles. Even this has been questioned. Yandell (1867) states “ that 
the relation of the disease to animal products is not on an impregnable 
