Plural form of fascilus, though this spelling is extremely rare or archaic; typically the plural of fasciculus is fasciculi.
This appears to be a non-standard Latin plural or variant spelling. Standard Latin pluralization of fasciculus would be fasciculi, making this form anomalous in medical literature.
Sometimes when tracking word variants in medical texts, you find oddball plurals that don't follow typical Latin rules—fascili might represent an alternative pluralization attempt or transcription error in older texts.
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