Figure 2. The brainstem trigeminal complex of an adult water shrew.

A. A single horizontal section of the brainstem showing the relative size and location of the trigeminal complex. The overall form of the complex is similar to that observed in rodents. The prominent trigeminal nerve (V) enters rostrally (rostral is up in “A”) and the trigeminal tract is evident at the lateral margins of the each complex. PrV, principal trigeminal nucleus. SpVo, spinal trigeminal subnucleus oralis. SpVi, spinal trigeminal subnucleus interpolaris, SpVc, spinal trigeminal subnucleus caudalis. B. A single coronal section from a juvenile (postnatal day 12) water shrew illustrating PrV bilaterally. PrV contained a prominent set of barrelettes. C. A single coronal section from a juvenile (postnatal day 8) water shrew illustrating SpVo bilaterally. No barrelettes are apparent. D. A single coronal section from a juvenile (postnatal day 8) water shrew illustrating SpVi bilaterally. As in rodents, the barrelettes in SpVi were larger and somewhat more prominent compared to those in PrV. E. A single coronal section from a juvenile (postnatal day 8) water shrew illustrating SpVc bilaterally. As in rodents, each barrelette was largest in SpVc. The full pattern of barrelettes was not obvious in single sections through SpVc due to the extreme curvature of SpVc in the coronal plane (see plate A). All sections processed for cytochrome oxidase. Plates C, D, and E are from the same juvenile case, plate B is from a case different from that in C, D, and E. Scales  = 1 mm in all plates. In A, caudal is down, in B–E dorsal is up.