Theodore Schwann

Theodore Schwann (many sources also spelled his name Theodor) was a man who lived in the 1800's and is remembered as a great scientist.  His actual scientific career only lasted five years!  And yet, in that short time (1834-1839), he made many very important discoveries in Biology and Physiology.

Source

Cell Theory
Shortly after German Botanist Matthias Schleiden discovered that plants are made of cells, Schwann discovered that animals are as well (Source).

Alcoholic fermentation
He hypothesized that fermentation wasn't a reaction with nitrogen in the air as people then believed, but that tiny organisms (yeast) were eating the sugars of the fruit and then excreting carbon dioxide and ethanol.  People in his day noticed yeast multiplied with fermentation, but he was the first to suggest they were the thing doing the fermenting, rather than just a byproduct of it.  He also stated that yeast were living plant-like organisms, firmly establishing fermentation as a biological process.  He was publicly ridiculed for this hypothesis which came at the end of his short career and probably helped lead to its demise, as he could no longer get funds or promotions to continue doing scientific research.  (Paraphrased from The Other Brain, by R. Douglas Fields, 2009, and Wikipedia- Theodore Schwann.) 

Digestion
He suspected that hydrochloric acid wasn't the whole story with digestion.  He discovered Pepsin, the enzyme that helps break down proteins (The Other Brain). He also showed that bile is essential to digestion, and coined the term "metabolism" describing chemical changes in animal tissue (Source).

Schwann cells
The myelinating cells in the Peripheral Nervous System are his namesake, since he first described them.  He studied nerves, noticing they had little dew-drop like structures running the length of them.  He thought that a neuron being built during development must join with other cells to create the long axon by fusion, and the Schwann cells were remnants of this process from those fetal cells.  Although his speculation was incorrect, these cells still carry his name.

Source

There's a brief summary of a great scientist's work.  I read about him in the book I've currently got my nose in (and hoping to finish before school starts back up), The Other Brain, by R. Douglas Fields.  It's all about Neuroglia, aka glia, glial cells.  To read an overview of all the types of Glia, go to this post: http://biogeonerd.blogspot.com/2013/08/neuroglia.html