16 
The Bulletin 
ence has previously been made, occurred during April and May. In 
the light of evidence to be presented later in this paper, there is no rea¬ 
son for believing that the disease may he limited to any one season. If 
it chances to be more prevalent in late summer and fall, as is commonly 
believed in this State, it can be accounted for by the refusal of animals 
to eat of the weed until this season of the year. A scarcity of more 
palatable plants through drought may compel them to eat more freely 
at this season of white snakeroot than is their custom. 
A considerable number of flowering plants have at various times been 
held to be the cause of trembles. Among them are the following: Rhus 
toxicodendron (poison ivy), Eupatorium urticaefolium (white snake- 
root), Lobelia inflata (Indian tobacco), Cicuta maculata (water hem¬ 
lock), Bigelovia Rusbyi (rayless goldenrod), Psedera quinquefolia (Vir¬ 
ginia creeper), Symphoricarpos orbiculatus (coral berry), Apocynum 
cannabinum (Indian hemp), Caltha palustris (marsh marigold), Eu¬ 
phorbia esula (leafy spurge), and Aethusa cynapium (fool’s parsley). 
Through the writings of Drake (1836 and 1841), Travis (1840), Crook 
(1857), Chase (1861), and Elder (1874), poison ivy was at one time 
quite generally accredited as being the cause of the disorder. Henry 
(1854) and Beach (1883) pointed out that horses, cattle, and sheep 
frequently eat the foliage of this plant with manifestly no ill effects. 
The connection of poison ivy with trembles is further opposed by Lan¬ 
drum (1861) and H. M. K- (1862), who assert that milksickness 
has never occurred in certain localities where poison ivy grows luxur¬ 
iantly. 
Claims that a number of other plants are the probable cause may 
be found in the accounts of McCall (1822), Short (1840), Fisher and 
Ivennicott (1861), and Allen (1878), hut these authors adduce little 
evidence in support of their conclusions. 
White snakeroot has probably been more commonly accused of being 
responsible for trembles than any other plant. As long ago as 1840 Dr. 
Barbee, who will be recalled as having first given information to Dr. 
Drake which led to the publication of the first account of the disease, 
expressed the opinion that this weed was the cause of the disease. A 
few years later Dewey (1854) stated that the disease is due to “a suc¬ 
culent plant bearing a white blossom.” He did not know the name of 
the plant and failed to have it identified, but it is very probable that he 
had reference to white snakeroot. Subsequently, evidence adduced by 
feeding experiments conducted by Vermilya (1858), Jerry (1867), 
Townshend (1883), and Moseley (1906) point to white snakeroot as 
the etiological factor in the production of milksickness. 
