From Wikipedia.
Santiago Ramón y Cajal (1852 – 1934) was a Spanish histologist, psychologist, and Nobel laureate. His pioneering investigations of the microscopic structure of the brain were original: he is considered by many to be the father of modern neuroscience. He was skilled at drawing, and hundreds of his illustrations of brain cells are still used for educational purposes today.
This
PAPER is a catalogue of his drawings and slides. In it the authors quote Cajal on how he did his drawings;
“The camera lucida, even when one is accustumed to its use through much practise, is only useful to fi x the contour of the principal objects: any labour of detail must be done without the aid of that instrument,
which has, in addition, the inconvenience of dazzling the delicate details….Reproduction by freehand drawing is the best procedure when one has some habit and liking for artistic painting”.
An example below - a drawing of Purkinje cells (A) and granule cells (B) from pigeon cerebellum by Santiago Ramón y Cajal, 1899. Instituto Santiago Ramón y Cajal, Madrid, Spain.