502 ANNUAL REPORT OF THE Off. Doc. 



tests conducted in wire baskets in a very considerable measure more 

 availal)le to plants than when in its original raw state. The Penn- 

 sylvania Agricultural Experiment Station is at the present, under 

 the writer's direction, conducting tests upon the effect of wet mixing 

 on inert nitrogenous substances, including peat, with the hope of 

 adding to our present knowledge upon this subject. 



REPOKT OF THE MICROSCOPIST AND HYGIENIST 



By PROF. JAMES W. KELLOGG 



A report of the work accomplished during the year must neces 

 sarily be confined more to microscopical examinations than to that 

 which might possibly be designated to the duties of a hygienist, or 

 the work which has to do with sanitary science and the preservation 

 of health. Your specialist has only been able to devote study to 

 microscopical work in connection with the examination of feeding 

 stuffs made by the Bureau of Chemistry of the Department of Agri- 

 culture, whose duty it is to examine these commodities for their 

 purity of composition. During the past year, we have been busily 

 engaged in this line of work and are able to report that the samples 

 examined were found to be as a whole greatly improved over those 

 examined during the previous year. 



The use of the microscope in investigations of this kind and in 

 studying nature is one of the most interesting branches of science. 

 The value of this instrument cannot be estimated, and the discoveries 

 made by its use are too numerous and too wonderful to endeavor to 

 describe here. The microscope has helped men of science to unlock 

 the secret of nature, to look into another world, the microscopical 

 world so to speak, and to discover new forms of life and small par- 

 ticles of matter which were never dreamed of before this valuable 

 instrument was perfected and as widelv used as it is todav. All 

 through the centuries men have unlocked nature's secrets one after 

 another, first, by a very crude instrument and later by improved 

 forms, until at the present time, the microscope is used in practically 

 all branches of scientific research, and in the business of the com- 

 mercial world. 



It was known by the Greek and Roman philosophers before the 

 time of Christ, that globes of crystal or lenses would focus the sun's 

 rays to a single point. Seneca states that ''letters though small and 

 indistinct are seen enlarged and more distinct through a globe of 

 glass filled with water." The ancient students, however, do not ajt- 

 pear to have made use of this phenomenon as an aid to vision, as in 

 the thirteenth century, medical writers seemed to be of the opinion 

 that it was impossible to cure short-sightedness. 



The first distinct advances in microscoi)y were made by the Arabian 

 physician, Alhazen, in the eleventh century. Near the end of the 

 thirteenth century, we learn that lenses were first used as a help to 

 defective vision, for we are told that Salvino Armati, a Floren- 



