Assertion: gray matter's neuron | /r/HasProperty | observed at same time
Facets:
value: in the early 19th century
type: TEMPORAL
value: probably
type: DEGREE
Source sentences:
text: Although glial cells and neurons were probably first observed at the same time in the early 19th century, unlike neurons whose morphological and physiological properties were directly observable for the first investigators of the nervous system, glial cells had been considered to be merely “glue” that held neurons together until the mid-20th century.