114 PASTORAL AND AGRICULTURAL BOTANY 



contain certain fractions of a milligram of protein-nitrogen. The lowest 

 dilution, i cc. of which may be used as the initial dose in treatment, 

 contains o.oo 25 mg. 



8. The final solutions are preserved from contamination by the addition 

 of 0.35 per cent, tricresol and sterilized by filtration. Sterility is deter- 

 mined by careful aerobic and anaerobic cultural tests. 



Vaccines.- Two kinds of vaccines have been prepared the ''spring" 

 and "fall." The hay-fever vaccine "spring" contains the varieties of 

 pollen which are the causative agents in the great majority of hay-fever 

 cases occurring in the late spring and early summer. The hay-fever 

 vaccine "fall" contains only proteins fiom the pollens of ragweed, golden- 

 rod and maize. For immunization against hay-fever, the first dose of 

 the vaccine in a syringe should be given 30 days before the expected attack 

 and the vaccine should be used weekly at intervals during the entire 

 period of accustomed attack or until immunity is established. 



Another preparation is pollantin, used as an antitoxic serum to secure 

 immunity against an attack of hay fever. 



Walnut Pollen as a Cause of Hay Fever. The spring type of hay fever 

 is very troublesome in the Sacramento Valley, California where it has 

 been found to be due to the pollen of the native Californian black wafnut 

 (Juglans calif ornica, var. Hindsii), which produces pollen in abundance 

 during the peiiod of the prevalences of the malady, which disappears 

 after the close of the flowering period. Biological tests were made upon 

 eight hay fever subjects with positive results in each case with the use 

 of walnut pollen. Twelve susceptible persons were examined at Chico, 

 where cases are common, and where the walnut is planted as an ornamental 

 tree, and in every case positive reactions were obtained with extracts 

 prepared from the Californian black walnut pollen. 



BIBLIOGRAPHY 



BOND, H. G.: Box Elder Poisoning. The Veterinary Alumni Quarterly, Ohio College 



Veterinary Medicine, 1916, in. 

 BOSTON GLOBE: Hay Fever Causes. Health Board puts Blame on Certain Types of 



Weeds. Boston, Sunday September 3, 1916, page 12. 

 CLARK, GEORGE H. and FLETCHER, JAMES: Farm Weeds of Canada. Illustrated with 



Colored Plates, Ottawa, 1906, pages 51, 52, 57. 

 Cox, HERBERT R.: Hay- fever Season is Here. Some Weeds that Make Folks Sneeze. 



The Country Gentleman, August 5, 1916, page 1467. 



