presumptive notochord

例句：

1. 1. The notochord is the central part of the spinal cord that connects the brain to the body.
   中轴是脊髓的中央部分，将大脑与身体连接起来。
2. 2. During embryonic development, the notochord helps form the vertebrae.
   在胚胎发育过程中，中轴有助于形成脊椎。
3. 3.In some species, the notochord can be modified to support additional structures.
   在某些物种中，中轴可以被修改以支撑额外的结构。