Location of pupillomotor and accommodation fibres in the oculomotor nerve: Experimental observations on paralytic mydriasis

Hutchinson (1867-68) in his 'Lectures on compression of the brain' was the first to indicate that with an acutely expanding intracranial mass, the ipsilateral pupil frequently dilated and became unresponsive to light. This he attributed to compression of the third nerve. Von Bergmann (1880) and subsequently Macewen (1887) came to similar conclusions re- garding the significance of paralytic mydriasis in determining on which side such lesions were to be found. These authors and most subsequent writers on the subject have favoured compression of the third nerve as the most likely mechanism.