Using special stains and microscopy, individual chromosomes are identified, and the presence of an extra chromosome 18 is revealed.
For microscopy the Fraunhofer formula is best written S =X/A.
The subject-matter of this new science, or branch of biological science, had been neglected: it did not form part of the studies of the collector and systematist, nor was it a branch of anatomy, nor of the physiology pursued by medical men, nor again was it included in the field of microscopy and the celltheory.
Wright, Principles of Microscopy (1906); W.
Spitta, Microscopy (2nd ed., 1909); Sir A.