Author Affiliations +
Vonnie D. C. Shields,1 Thomas Heinbockel2
1Biological Sciences Department, Towson University, 8000 York Rd., Towson, MD 21252, E-mail vshields@towson.edu
2Department of Anatomy, Howard University College of Medicine, 520 W St., NW, Washington, DC 20059, E-mail theinbockel@howard.edu