Neural and hypophyseal colloid deposition in the collared lemming.

Feral and captive lemmings from Churchill, Manitoba, are subject to a unique pathological process in which colloidal material is deposited in bloodvessel walls at scattered points through the central nervous system. Destruction of nervous tissue at these foci is progressive, and colloidal masses in the vascular lumina of the hypothalamus appear to become fixed in the capillaries of the hypophyseal anterior lobe. Inflammatory reactions are never associated with the lesions, and the latter are larger and more numerous in older animals in warmer environments.