Ant colonies > Internal structure of ants > Sympathetic

Sympathetic


The Sympathetic

This consists of several minute ganglia and nerves connected with the central nervous system and supplying the musculature of the alimentary tract. It is, to judge from Janet's account of Myrmica (1902), well developed in ants and not unlike that of other insects. It may be said to embrace two systems, one supraintestinal and supplying the dorsal and lateral portions of the digestive tract, the other subintestillal and lying beneath the intestine and above the ventral nerve-cord. The supraintestinal system may be divided into an unpaired and a paired portion. The former begins in the small frontal ganglion (Fig. 27, fgl), which lies anterior to the brain, to which it is joined by a pair of connectives. According to Janet, these connectives arise in the protocerebrum, but other authors believe that they are of tritocerebral origin.

The frontal ganglion sends a pair of coalesced nerves to the supero-anterior wall of the pharynx and a much stouter unpaired nerve, known as the recurrens (yen), downward and backward along the dorsal wall of the pharynx, to a ganglion (the hypocerebral, hcs), which lies on the oesophagus just beneath the protocerebrum. Besides innervating the oesophagus this ganglion sends back a pair of long, slender connectives (syni) along the sides of the oesophagus and crop to the point where the latter contracts to form the gizzard. Here each connective terminates in a so-called pre-stomachal ganglion, which innervates the sur­rounding wall of the crop and gizzard. The paired supraintestinal sympathetic has an anterior and a posterior portion.

The former con­sists of the oesophageal ganglia, which lie on each side of the hypo­cerebral ganglion. They are united with this by commissures and with the tritocerebrum by connectives, and innervate the sides of the oesoph­agus and crop. The posterior portion of the paired system is very imperfectly known. Janet maintains that the fourth pair of nerves from the terminal ganglion of the ventral cord turns forward and innervates the posterior portion of the digestive tract in somewhat the same manner as the anterior portion is innervated by the brain through the frontal and oesophageal ganglia. He, therefore, calls these the proctodaeal recurrent nerves. The subintestinal sympathetic system of hlyrmica comprises a series of minute, unpaired, metameric ganglia connected with several of the ganglia of the ventral cord. This system, too, both in ants and in other insects, is imperfectly known.