370 ANNUAL REPORTS OF DEPARTMENT OF AGRICULTURE. 



substances represent the active constituents which nsnally must be 

 isolated by involved methods of liquid extraction, precipitation, and 

 purification. Less material, time, and money is needed if these sub- 

 stances can be isolated by sublimation. The quantity of material 

 submitted for identification or examination is often limited. Atten- 

 tion has therefore been given to the development of sublimation. 

 Extensive data on macrosublimation and microsublimation have 

 been collected from the literature. Waste products of plant and 

 animal origin have been examined, with striking success. It is 

 found that the active substances usualh^ can be obtained in a pure, 

 or practically pure, state by fractional sublimation, preferal)ly using 

 diminished pressure. Apparatus for sublimation, microsublimation, 

 and micromelting-point cleterminations, and an electrically heated 

 oil bath have been developed. 



A study was made of the occurrence and distribution of hydro- 

 cyanic acid or cyanogenetic compounds in plant products. Many 

 products would be safely available for food or feed purposes but for 

 the fact that they may develop hydrocyanic acid (prussic acid) in 

 injurious quantities. One species {Phaseolus lunatus) yields many 

 varieties of beans, all of which produce hydrocyanic acid upon mac- 

 eration of the bean meal. Fortunately, domestic forms yield such 

 small quantities that the}^ can be consumed without danger. Many 

 tropical varieties have been found to contain dangerous quantities. 

 Detailed anatomical, chemical, and morphological data, which will 

 be lielpful in effecting an efficient control of the seeds, have there- 

 fore been collected. There is much evidence that the quantity of glu- 

 coside formed in the beans is an inherited factor and is characteristic 

 of the particular strain. 



Similar work is being carried out with seeds of bird's-foot trefoil, 

 to be introduced by the Bureau of Plant Industry as an early forage 

 crop. The plants tested thus far have yielded dangerously large 

 quantities of hydrocyanic acid. The aim is to follow the procedure 

 adopted -in the study of Phaseolus lunatus, in the hope that strains 

 of seed yielding such small quantities that the plants may be grown 

 as a safe forage crop may be obtained. 



It was found that the inert and objectionable material in crude 

 drugs and spices can be removed effectively by selective siftings. 

 A study was made of green and roasted coffee to develop means for 

 the identification of coffee as to origin. During the year data were 

 collected in connection with the revision of the United States Phar- 

 macopoeia and National Formulary. 



PHARMACOLOGICAL INVESTIGATIONS. 



The pharmacology of zinc, tin, and other heavy metals is being 

 studied. Data which show the comparative toxicity of the metals 

 are being collected. One of the purposes of this work is to develop 

 new criteria by which toxicity may be studied and to make results of 

 animal experiments more useful in setting food standards. A tox- 

 icity study of various arsenical insecticides was made. The results 

 indicate that the insecticides can be considered practically as toxic as 

 inorganic arsenious oxide. Results of work on the pharmacologj' of 

 cadmium and zinc were published during the year. 



