text: who is johannes purkingco?   i'm pretty sure you mean johannes evangelista purkinje.  he was professor of physiology at the university of prague, where he discovered the phenomenon known as the pukinje effect (as light intensity decreases, red objects are perceived to fade faster than blue objects of the same brightness).   he is best known for his discovery, in 1837, of purkinje cells, large nerve cells with many branching extensions found in the cortex of the cerebral cortex. he is also known for his 1839 discovery of purkinje fibers, the fibrous tissue that conducts the pacemaker stimulus along the inside walls of the ventricles to all parts of the heart. purkinje introduced the scientific terms plasma, to describe the clear liquid remaining after blood has been cleared of it’s various corpuscle components, and protoplasm, used to describe young animal embryos.   purkinje was the first to use the microtome (to slice thin tissue sections), glacial acetic acid, potassium bichromate and canada balsam in the preparation of tissue samples for microscopic examination. purkinje described the effects of camphor, opium, belladonna and turpintine on humans in 1829. an early user of the improved compound microscope, he discovered the sweat glands of the skin in 1833, germinal vessicles in 1825, recognized fingerprints as a means of identification in 1823 and noted the protein-digesting power of pancreatic extracts in 1836.   johannes evangelista purkinje was a pioneer to experimental physiology whose investigations in the fields of histology, embryology and pharmacology helped to create a modern understanding of the eye and vision, brain and heart function, mammalian reproduction and the composition of cells.