118 ANNUAL REPORTS OF DEPARTMENT OF AGRICULTURE. 



The western sneezeweed (Dugaldia Tioopesii) has been shown to be 

 the cause of the "spewing sickness" of sheep. The extended study 

 of the subject was found to be quite comphcated, but it is now nearly 

 completed. A glucosid has been separated, which is the cause of the 

 disease, and its pharmacology has been studied. The pathological 

 results of the poisoning have been worked out. 



An investigation of a heavy loss of sheep on the Sevier National 

 Forest in the summer of 1917 threw suspicion on Gutierrezia diversi- 

 olia (yellow weed), and feeding experiments confirmed the suspi- 

 cion. It is now known that this plant, which is not ordinarily 

 considered poisonous, may, under certain circumstances, cause 

 heavy losses. The detailed examination of the plant is being car- 

 ried on. 



Astragalus diphysus, a loco plant which is common in southern 

 Utah, Arizona, and New Mexico, has been supposed to be poisonous, 

 but with no definite proof. In the past season it has been proved 

 that it will " loco " cattle and horses, and it is thus added to the number 

 of plants which are definitely known to be locoes. 



Asclepias verticillata, the whorled milkweed, has been under 

 suspicion for several years, but has not been generally recognized 

 as a poisonous plant. Recent experiments have shown that it is 

 exceedingly toxic and doubtless has been the cause of heavy losses, 

 more especially of sheep. Not only have corral experiments been 

 conducted on this plant, but the chemical examination is well under 

 way. 



It has been found that the lupines, of which there are a large 

 number of species, differ in their toxicity, and there is reason to 

 think that many of them are entirely harmless. To discover by 

 feeding experiments which species are poisonous would be a long 

 and tedious task. Therefore a chemical examination of the toxic 

 principles in the lupines has been undertaken and progress has already 

 been made. It is hoped by this means eventually to classify these 

 plants in accordance with their toxicity. 



Work on Eupatorium urticaefolium (white snakeroot or rich weed), 

 Zygadenus (death camas), Ilymenoxys ligutaefolia (rubber weed), and 

 Aconite has been continued. A preliminary examination of Dauhen- 

 tonia longifolia showed that this plant, which grows in Texas, is toxic. 



BIOCHEMIC DIVISION. 



The work of the Biochemic Division, under M. Dorset, chief, con- 

 sisted principally of investigations concerning hog cholera, laboratory 

 research work relating to meat products, studies of dips and dis- 

 infectants, and the preparation of tuberculin and mallein. 



HOG-CHOLERA INVESTIGATIONS. 



The investigative work on hog cholera has related to (1) methods 

 of producing immunity from the disease and (2) modes of its spread, 



METHODS OF PRODUCING IMMUNITY FROM HOG CHOLERA. 



During the year the ])ean-extract-=!alt method has been used to 



Erepare more than 100,000 cubic centimeters of serum, the object 

 eing to determine the practicabiUty of the method. The clear 



