In general, spiders have a nervous system that resembles that of vertebrates except that it is much less elaborate, especially in regard to intellectual functions. The structures that comprise the cellular masses of a spider's nervous system are almost entirely found in the cephalothorax with just a few relatively minor ganglia (clumps of nerve cells) in the abdomen. The piece of neurological tissue that serves as a spider's brain is the supraoesophageal ganglion which is positioned just above the digestive tract and in front of the sucking stomach. Present evidence indicates that the most important function of this brain is to process sensory information, especially that from the eyes, and to produce suitable responses, including movements of the chelicerae and the release of venom from the venom glands. these responses are obviously important for survival and a spider's brain does appear to have at least a small capacity to learn from past experiences and to respond more appropriately when dealing repeatedly with the same set of circumstances.