1885.] NEW-YORK MICROSCOPICAL SOCtETV. 211 



tinue an enigma ; its law of work, however, may yet become 

 fully known, and this fulness of knowledge may better incalcu- 

 lably man's estate. 



But biology owes its existence to the microscope, and to that 

 instrument must it look for its progress and its triumphs. And 

 what, in its present state, is this instrument, with its immediate 

 accessories, and all its various kinds of subsidiary apparatus ? 

 and what the scope and quality of intelligence, of knowledge, 

 of training of eye and hand, embraced in its mastery ? To this 

 question, the story, however simply told, of the work performed 

 by Dr. Koch in his studies of bacterial life, or by Drs. Dallinger 

 and Drysdale in their researches on the origin and life-histories 

 of the " least and lowest of living things," would be a grand and 

 sufficient reply. 



There is, then, a science of microscopy. Its mastery is peculiar- 

 ly difficult, requiring rare sagacity and dexterity, and a lifetime 

 of devotion, and its study has become a profession. This fact 

 is not known to all, it having grown too fast for any but a 

 watchful eye to keep pace with it. " There is no science of 

 microscopy — the microscope is only an instrument," was said in 

 our hearing a few days ago. A gun is but an instrument ; yet is 

 there not a science of gunnery ? and its acquisition is an in- 

 dispensable part of the professional soldier's education. The 

 importance of a special and systematic course of instruction in 

 microscopy is gaining recognition in some of our best institu- 

 tions of learning. 



Micrometry and Blood-Corpuscles. — No microscope is 

 complete unless equipped with ample and accurate means of 

 micrometric measurement, and no man who does not fully un- 

 derstand the use of those means is entitled to be called a pro- 

 fessional microscopist. He who possesses this accomplishment 

 has facilities for adding valuable material to the stock of human 

 knowledge. The careful measurements made by Dr. Ewell, of 

 Chicago, of the diameters of human blood-corpuscles may yet 

 prove of inestimable service in some cases of medical and crim- 

 inal jurisprudence. Where the issue of life and death is involv- 

 ed, Dr. Ewell declares it reckless, if not criminal, to express an 

 opinion upon a measurement of fewer than one hundred cor- 

 puscles. 



