Page:Laboratory Manual of the Anatomy of the Rat (Hunt 1924).djvu/125

Rh if they be severed at their union with the cerebellum by a horizontal stroke with a sharp razor.

Clear away the tissue on the dorsal and lateral side of the cerebral hemisphere, exposing the corpus callosum. Trace it into the hemisphere. Cut through the corpus callosum, expose the cavity of the hemisphere (lateral ventricle), and open this ventricle throughout its extent. The anterior horn of the ventricle runs ventrally, bounded medially by the septum pellucidum, and laterally by the convex corpus striatum. The remainder of the cavity follows a curvilinear course, at first posteriorly and laterally, and finally ventrally, terminating near the infundibulum. From the corpus striatum backward the hippocampus forms the median wall of the ventricle. The lateral surface of the hippocampus is convex. Viewed from above it forms an angle of about forty-five degrees with the long axis of the brain; from the side it is approximately U-shaped. The lateral and third ventricles communicate through the interventricular foramina (foramina of Munro).

Exercise XXIX. Sketch a sagittal section of the brain.

The sympathetic nervous system regulates the distribution of blood in the body through its control over the nonstriated muscle tissue in the walls of the blood vessels. This regulation is accomplished through variation in the calibre of the vessels, brought about by the contraction and relaxation of these muscles. Sympathetic fibers innervate also the respiratory, reproductive, digestive, and other organs, together with their glands. The motor activities of the system are beyond the control of the will, and the stimulation of its sensory structures does not necessarily induce conscious states.