Succus entericus is referred to as :

The correct answer is Intestinal juice.

Explanation:
Succus entericus is the medical and biological term used to refer to the digestive secretion produced by the glands lining the walls of the small intestine. Specifically, it is secreted by the mucosal epithelium, which includes the goblet cells (secreting mucus) and the brush border cells of the mucosa (secreting various enzymes).
Let us break down the options to understand why this is the correct choice:

1. Intestinal juice (Succus entericus): This alkaline fluid contains a mixture of water, mucus, and digestive enzymes such as maltase, lactase, sucrase, peptidases, and nucleosidases. It works in the small intestine to complete the digestion of carbohydrates, proteins, and lipids.
2. Pancreatic juice: This is secreted by the pancreas and released into the duodenum. While it contains crucial enzymes like trypsinogen, amylase, and lipase, it is distinct from succus entericus.
3. Gastric juice: This is the highly acidic digestive fluid secreted by the glands of the stomach, containing hydrochloric acid (HCl) and pepsinogen.
4. Chyme: This is the semi-fluid mass of partially digested food and gastric juices that passes from the stomach into the small intestine, rather than a specific glandular secretion.

Therefore, succus entericus is synonymously referred to as intestinal juice.