Hydranencepha* (mrmotensive hydrocephalus) is an absence of cerebral hemispheres in a cranium of normal conformation. John Pringle -ORDERS nervous system of domestic animals. Most defects are lethal and are diagnosed at ne- cropsy. Causes may include genetic or environmental factors. Environmental factors are highly varied and include teratogens, viruses, drugs, trace elements, and physical dam- age (e.g., rectal palpation of the dam). OF THE NEWBORN. There are many congenital defects of the -