Marshall[140] studied the loco question with regard to sheep and practically denies the existence of a locoed condition due to eating the loco plants, but believes the condition due to bad feeding, parasitism, etc. He lays great stress upon the presence of worms, but fails to see that they may be merely a secondary infection superimposed upon an already morbid condition produced by eating the plants. Others have claimed that the cause is an insect living upon the loco plants. Others, again, have suggested an analogy with trypanosome disorders. Chesnut has held the view that many of the cases of so-called locoed sheep were really due to parasites, but that there was a true locoed condition due to eating the loco weeds. The lack of agreement in the results of the investigators has caused many to doubt any positive relation between the plant and the disease, and even as late as 1904 Payne[141] practically says these diseases are due to lack of nutrition and not to the loco plant. The matter has been summed up in a recent work as follows: Though many chemists have sought for the constituents, none have been able to locate the active properties, the trace of alkaloids, resins, volatile and fixed oils having each in turn been found destitute of it. Yet the poisonous properties are fully established by field observations. The destructiveness of these plants to stock is so great as to have probably caused upward of a million dollars loss in the aggregate, and large bounties have been offered by State governments for an effective method of avoiding such losses. It is considered very probable that the poisonous constituent is albuminoidal.[142] * * * * * FOOTNOTES: [83] Storke, B. F. The Loco Weed. Med. Current, vol. 8, p. 155. 1892.--Kellogg, A. California and Colorado "Loco" Poisons. Cal. Acad. Sci. Proc. for 1875, vol. 6, p. 3. 1876. NOTE.--The very early reports of these loco plants were purely botanical. See Torrey, J., Botany, in Report on the United States and Mexican Boundary Survey, by W. H. Emory, vol. 2, p. 56, 1859; also Botanical Register, London, vol. 13, pl. 1054, 1827. [84] Vasey, G. Plants Poisonous to Cattle in California. Rept. of Commissioner of Agriculture for 1874, p. 159. 1875. [85] Vasey, G. Botanical Notes. Monthly Reports of Dept. Agriculture for 1873, p. 503. 1874. [86] Vasey, G. Botanical Notes. Monthly Reports of Dept. Agriculture for 1874, p. 513. 1875. [87] Brewer, W. H., and Watson, S. Geological Survey of California, Botany, vol. 1, p. 155. 1876. [88] Rothrock, J. T. Notes on Economic Botany, in G. M. Wheeler's Report upon U. S. Geographical Surveys West of the One Hundredth Meridian, vol. 6, p. 43. 1878. [89] Kellogg, A. California and Colorado Loco Poisons. Cal. Academy of Sciences, Proc., 1875, vol. 6, p. 3. 1876.