Nerve Fibers within the Gastrointestinal Tract in Mice R. M. OESSER,12* AND S. C. KOOI Division of Allergy, Itnnuutology. and Infectious Diseases, The Children's Hospital of Philadelphia,' and The Wistar Institute,' Philadelphia, Pennsylvania 19104 Received 27 December 1995/Accepted 28 February 1996 Herpes simplex virus type I (HSV