LESSON XXXI. 



THE SPINAL CORD. 



1. Transverse sections of human spinal cord through 

 the cervical swelling, the mid-thoracic region and 

 the lumbar swelling (e.g. 6th C., 6 Th., 4th L.) (potas- 

 sium bichromate, cut frozen, picrocarmine). Mount in 

 balsam. Comparison of the sections will be easier if 

 they are mounted on the same slide. Observe the 

 following general features of the spinal cord, first under 

 a low and then so far as is necessary under a high 

 power. 



The pia mater, of connective tissue surrounding 

 the cord ; it sends into the cord numerous septa. Note 

 the blood vessels running from the pia mater into the 

 cord along the septa. 



The anterior and posterior fissures; the pia 

 mater folds down into the anterior fissure ; it sends a 

 septum only into the posterior fissure. 



The exit from the cord of the anterior roots 

 of the spinal nerves ; they are seen as several small 

 inconspicuous bundles running longitudinally through 

 the white substance. 



The entrance into the cord of the posterior roots 

 of the spinal nerves in a compact mass. 



