436 ANNUAL REPORTS OP DEPARTMENT OF AGRICULTURE. 



terants for niire gum tragacanth, it was found that the amount of 

 volatile aciu (acetic acid) generated on treatment with dilute phos- 

 phoric acid and subsequent distillation with steam could be used 

 as an indicator of the j)urity of such gums, inasmuch as the Indian 

 varieties yield approxunately seven times as much volatile acid as 

 pure gum tragacanth. 



ESSENTIAL OILS. 



Durmg the year 163 samples of essential oils have been submitted 

 to examination in this laboratory; of this number 15 were reported 

 as adulterated or misbranded. A number of unollicial samples of 

 oils have been examined with the object of determining- the best 

 methods for their analysis, especially with respect to the determina- 

 tion of the ketones and aldehydes by the hydroxylamin titration 

 method. A variety of samples have been submitted to this laboratory 

 for check analysis, includmg both import and interstate samples of 

 essential oils, as well as samples of cod liver oil compounds, spirits 

 of camphor, etc. 



A chemical investigation of oil of chenopodium has been carried 

 on, having in view especially the extension of our knowledge of the 

 properties of the peculiar medicinal^ active ingredient, ascaridol. 

 The results of this investigation, so far as completed, are to be found 

 in Chemistry Circular 73. 



PHARMACOLOGICAL INVESTIGATIONS. 



These investigations were devoted largely to the pharmacology of 

 caffein and were conducted along the following lines: 



(1) Research work on the comparative toxicity of caffein in dif- 

 ferent species of animals. The results have been compiled. 



(2) A number of experiments on the toxicity of caffein under 

 pathological conditions, with additional work on the effects of feeding 

 caffein over long periods of time, i. e., chronic caffein intoxication 

 in cats, dogs, and rabbits, both in normal and in fasting animals. 



(3) The work on caffein glycosuria has been practically completed. 



(4) The study of the alleged destruction of caffein by the liver has 

 been completed; no destruction of caffein was observed. 



(5) The effect of caffein on protein metabolism in dogs was also 

 concluded. The results obtained show that protein metabolism is 

 not disturbed to any extent during the administration of the drug, 

 although symptoms of caffein intoxication were manifested. When 

 caffein was withdrawn, however, there was a marked increase in the 

 elimination of nitrogen. 



(6) The study of the elimination of creatin and creatinin in rabbits, 

 begun in the previous year, was concluded. It was found that caffein 

 stimulates the elimination of creatin, but has no effect on the crea- 

 tinin. 



(7) Additional experiments on the circulatory changes produced 

 by caffein were made, but this work has not been completed. 



(8) The demethylation of caffein in the body has been studied 

 during the past year in rabbits and dogs, under normal and under 

 pathological conditions. The results indicate retarded demethyla- 

 tion in chronic alcoholism in rabbits. 



