Henry Gray (18251861). Anatomy of the Human Body. 1918.
appears in the region of the mid-brain, and is named the ventral cephalic flexure(Fig. 650). By means of it the fore-brain is bent in a ventral direction around the anterior end of the notochord and fore-gut, with the result that the floor of the fore-brain comes to lie almost parallel with that of the hind-brain. This flexure causes the mid-brain to become, for a time, the most prominent part of the brain, since its dorsal surface corresponds with the convexity of the curve. The second bend appears at the junction of the hind-brain and medulla spinalis. This is termed the cervical flexure(Fig. 652), and increases from the third to the end of the fifth week, when the hind-brain forms nearly a right angle with the medulla spinalis; after the fifth week erection of the head takes place and the cervical flexure diminishes and disappears. The third bend is named the pontine flexure(Fig. 652), because it is found in the region of the future pons Varoli. It differs from the other two in that (a) its convexity is forward, and (b) it does not affect