Dorsal root projections in various types of reptiles.

The distribution of dorsal root fibers into the spinal cord as well as to the brainstem have been studied in various types of reptiles. At the site of entrance into the spinal cord no clear segregation of large fibers medially and smaller fibers laterally has been observed. A peculiarity for reptiles seems to be a lateral bundle of primary afferent fibers which traverses the dorsal part of the lateral funiculus. The fibers of this bundle enter the spinal gray at the lateral side of the dorsal horn. Notable variation in the distribution of dorsal root fibers has been observed in the reptiles studied. In the turtle Testudo hermanni and in the snake Python reticulatus almost no fibers were found to extend into the ventral horn. However, in the lizard Tupinambis nigropunctatus a distinct projection into the ventral horn was observed. This closer potential coupling between the primary input and output systems of the spinal cord than in the turtle Testudo hermanni seems to be related to the long multijointed digits in the lizard studied which give its limbs a marked prehensile character.