2 BULLETIN 800, TJ. S. DEPARTMENT OF AGRICULTURE. 
poisoning in western Colorado, and described experiments in feed- 
ing sheep and rabbits which demonstrated the poisonous character 
of the plant. 1 
In preceding years, however, the Department of Agriculture had 
received many reports of losses of live stock from milkweed. In 
most cases the species of plant which caused the trouble was not 
indicated and the reports were so indefinite that the evidence was 
not considered strong enough to warrant the addition of the plant 
to the list of stock-poisoning plants. The reports came from not 
only Colorado but also from New Mexico, Arizona, California, and 
Oregon. In 1902, J. C. Johnson, of Higbee, Colo., reported the loss 
of horses from Asclepias verticUlata. 
In October, 1909, Dr. W. E. Howe, inspector in charge of the 
Denver district, received from Dr. S. C. Babson details of heavy 
losses of sheep in the neighborhood of Montrose, Colo. The losses 
were said to have been due to Asclepias verticUlata,, inasmuch as the 
animals had fed extensively on the plant and it was found in abun- 
dance in the stomach contents. Post-mortem examinations were 
made, and he reported as the only lesion " pale heart muscles, ex- 
cessive amount of pericardial fluid, and acute inflammation of the 
outer covering of the surfaces of the brain." 
A similar report was made by Dr. Babson to the chief of grazing, 
Forest Service, Denver, Colo. He said that the plant grew on the 
banks of irrigation ditches and that it had been traced from the 
beginning of the Montrose and Delta Canal to the California mesa. 
He stated, however, that the plant had leaves 3 or 4 inches long 
and in pairs. From the description it was assumed that the plant 
had been wrongly determined and that probably the species he had 
in mind was Asclepias speciosa. Some experimental work was under- 
taken in regard to Asclepias speciosa without any definite results. 
The attention of the "Washington office was again called to the 
matter by a letter from L. F. Kneipp, district forester, who reported 
losses of stock from Asclepicts suhulata near Diamond Valley on the 
Dixie National Forest and asked for an investigation. A package 
of the plant, which was said to have killed a great number of cattle 
on the Dixie Forest, was sent to the Bureau of Plant Industry for 
investigation, but on account of the small quantity of material it 
was impossible to determine whether the plant was poisonous. The 
accounts of the losses of animals on the Dixie Forest, however, were 
so definite that it was planned to make a more thorough field ex- 
amination. Meantime, in 1910, Mr. Balthis, supervisor of the Alamo 
National Forest, sent in specimens from Alamogordo, N. Mex., 
1 In the Amer. Jour, of Vet. Med., Vol. XIV, pp. 135-136, Dr. L. H. Pammel, in ad- 
dition to a review of the bulletin by Glover, Newsom, and Robbins, reports the treatment 
used by a local veterinarian on sheep poisoned by whorled milkweed near Hotcbkiss, 
Colo. 
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