The Abdominal and Pelvic Brain
Byron Robinson, M. D.

One's rainbow of desires changes color with the passing years.

"Instead of condemning me to death the city (Athens) should grant me a pension."
     The defense presented by Socrates in his trial.


    The plexus of the abdominal aorta extends from the coeliac artery to the aortic bifurcation.  It extends from the abdominal brain to the hypogastric ganglion or disc.  At the proximal end of the aortic plexus is located the abdominal brain, at the distal end is located the hypogastric ganglion or disc.  It consists of a wide meshed network of anastomosing nerve bundles and ganglia.  The main nerve cords, two in number, course parallel to the lateral borders of the abdominal aorta, constituting the aortic plexus, anastomosing with each other by means of nerve strands coursing obliquely or transversely ventral or dorsal to the aorta, and also with the lateral chain of lumbar ganglia by means of short nerve cords.  The plexus aorticus practically ensheaths the aorta, especially ventrally, with a wide meshed network of nerves and ganglia.

(a) The Ganglia of the Plexus Aorticus.

    The ganglia of the aortic plexus are numerous and important, being located practically at the origin of visceral vessels from the aorta.  They consist of multiple bordered, irregularly flattened bodies located mainly on the ventral and lateral borders of the aorta.  Originally the aortic plexus consisted of a bilateral gangliated cord located along the lateral aortic border, each ganglion representing the origin and mission of a visceral vessel.  By evolutionary processes and change of attitude the ganglia become removed, changed from this original site which was at the origin of the arterial vessels.  In general the ganglia of the plexus of the abdominal aorta are located at the exit of the visceral vessels from the aorta abdominalis, viz.: (a) ganglion diaphragamaticum (paired), located on the proximal border of the abdominal brain in the form of a conical projection simulating the olfactory bulbs of the cranial brain; (b) ganglion coeliacum (unpaired), located at the origin of the coeliac, superior and inferior mesenteric and renal arteries; (c) Ganglion renalis, located at the origin of the arteria renalia; (d) ganglion ovaricum (paired), located at the origin of the arteria ovarica; (e) ganglion mesentericus inferior (unpaired), located at the origin of the arteria mesenterica inferior; (f) ganglion hypogastricum (unpaired), a coalesced disc located at the origin of the arteria iliacacommunicus at the aortic bifurcation.  The hypogastric ganglion, or disc, arises at the bifurcation of the abdominal aorta.  Its existence is according to the rule (modified by environments and erect attitude) that a sympathetic ganglion occurs at the exit of the abdominal visceral arteries from the aorta abdominalis.
    The position of the ganglia appears to have experienced changes with evolutionary development as they become transported by detachment from the base of the visceral artery toward the corresponding viscus or along bones and muscles.  Some visceral arteries, like the renal, possess a wealth of separate ganglia.  The ganglia are located in general: (a) at the origin of the visceral artery from the aorta; (b) along the lateral borders; (c) on the ventral surface of the vessel.  The ganglia mainly surround the root of the visceral vessel like a collar or fenestrated sheath and encase it towards its viscus with a plexiform network of nerves.
    The dimension of the ganglia in the aortic plexus practically correspond with the volume of the corresponding visceral artery.  The longest ganglion is that of the arteria coeliaca.  The smallest constant ganglion is perhaps that at the base of the arteria diaphragmatic.
    The form of the ganglia are oval, triangular or multiple bordered flattened bodies. The surface of the ganglia are uneven, with irregular, fenestrated spaces and occasionally perforated by blood vessels.

(b) The Nerve Trunks and Cords of the Plexus Aorticus.

    The ganglia of the aortic plexus are united or anastomosed into a wide meshed plexus by two general methods: (1) By two trunk cords extending along the lateral borders of the aorta from the ganglion coeliacum to the ganglion hypogastricum or hypogastric discs; (2) by cords of smaller and larger caliber coursing irregularly from ganglion to ganglion, from cord to cord and from one lateral trunk to the other.  The plexus aorticus is solidly and compactly united to the bilateral chain of lumbar ganglia by short, strong strands and to all visceral nerve plexuses of the abdomen.
    The plexus aorticus practically ensheaths the abdominal aorta (especially lateral, and ventrally) with a plexiform network of nerve cords and ganglia. From the plexus aorticus abdominalis arise: (a) the plexus diaphragmaticus (paired), which accompanies and ensheaths the arteria diaphragmatica (the right possesses a ganglion); (b)plexus coeliacus (unpaired), which accompanies and ensheaths the arteria gastrica (supplying the stomach), hepatica (supplying the liver) and lienalis (supplying the spleen); (c) the plexus mesentericus superior (unpaired), which accompanies and ensheaths the arteria mesenterica  superior with a network of nerve cords and ganglia to supply the enteron, right colon and right half of transverse colon; (d) plexus renalis (paired), which accompanies and ensheaths the arteria renalis with a network of nerve cords and wealth of ganglia to supply the kidney and proximal ureter; (e) plexus ovaricus (paired), which accompanies and ensheaths the arteria ovarica with a network of nerve cords and ganglia to supply the ovary, oviduct and ligament a lata; (f) plexus mesentericus inferior (unpaired), which accompanies and ensheaths the arteria mesenterica inferior with a mesh-work of nerves and ganglia to supply the right half of the transverse colon, right colon, sigmoid and rectum; (g) plexus hypogastricus (unpaired coalesced) which originally accompanied and ensheathed the arteria hypogastrica with a network of nerve cords and ganglia to supply tractus genitalis (especially the uterus and vagina) and distal segment of the tractus urinarius (especially the bladder and distal segment of the ureter).  The plexus aorticus abdominalis includes the abdominal aorta from the coeliac axis to its bifurcation on the sacral promontory, hence its profound connection to every abdominal visceral tract through the arteries.  The vital signification of the plexus aorticus abdominalis is at once evident when it is observed that from it issues practically nine great visceral arteries (the coeliac, two mesenteric, two renals, two ovarian and two iliacs) accompanied by great nerve plexuses and having at least one marked sympathetic ganglion at their origin.  Each of the eight nerve plexuses of the plexus aorticus are solidly and compactly anastomosed with every other plexus and connected with all other abdominal plexuses, making a compact network of abdominal sympathetic nerves perfectly planned to report functions to the ruling potentate, the abdominal brain.


    The physiology of the plexus aorticus abdominalis comprises the function of the viscera to which it supplies nerves viz.: tractus intestinalis, urinarius, genitalis, vascularis and lymphaticus.  The three great common functions of the abdominal viscera are: (a) Peristalsis, absorption, sensation and secretion.  To the common functions must be added for the tractus genitalis, (d) ovulation; (e) menstruation; (f) gestation.  We unconsciously employ the physiology of the aortic plexus in the practice of obstetrics or uterine hemorrhage.  When, after parturition, there is undue bleeding the physician attempts to check it by compressing the aorta.  He is in error for what the practitioner really performs is to irritate the aortic plexus and this results in exciting uterine contraction, the uterine muscular and elastic bundles act like living ligatures which limits the lumen of the vessels.  In irritating the aortic plexus no trauma or roughness need be employed.  Simple, light stroking of the abdomen or gentle kneading will quickly stimulate the aortic plexus which sends branches to supply the uterus through the pelvic brain, inducing it to contract and check haemorrhage.  The peristalsis of labor may be hastened by administering hot drinks to the patient.  The heat in the stomach stimulates the aortic plexus through the gastric plexus and consequently the nerves which supply the uterus inducing more vigorous and frequent uterine rhythm.  Friction on the nipple or massage of the breasts will induce more frequent and vigorous uterine rhythm during labor.  The stimulation from the mammae travels to the abdominal brain (and consequently to the aortic plexus and uterus) over the nerve plexus accompanying the mammary, intercostal, inferior epigastric arteries.  In abdominal massage we apply practical physiology to the various abdominal visceral tracts.  For example in constipation one or all the great visceral functions (peristalsis, absorption, sensation and secretion) are defective.  By stimulating the aortic plexus through massage intestinal peristalsis, secretion and absorption are enhanced as the irritation passes over the gastric plexus to the stomach over the superior mesenteric plexus to the enteron and over the inferior mesenteric plexus to the colon.  Constipation may be cured by massage of the abdomen.  Massaging the abdominal brain induces more active renal peristalsis, absorption and secretion.  The physiology of the sympathetic presents a vast field for future therapeutics, especially in the direction of visceral massage.  The massage of the abdominal sympathetic (plexus aorticus) will assume three directions of physiologic utility, viz.: (a) The great ganglia of the plexus aorticus will be stimulated, that is, the ganglion at the root of each visceral artery will be stimulated, which will excite the pulsating vessel (and the heart), supplying more blood to its corresponding viscus and consequently individual and collective visceral peristalsis, absorption and secretion is enhanced - this is administering a vascular tonic.  It also aids visceral drainage which consists in elimination of waste laden blood and lymph products.  In short, massage of the plexus aorticus abdominalis enhances visceral function (rhythm) and visceral drainage (elimination); (b) massage of the plexus aorticus enables the operator to manipulate each, individual, viscus which not only excites the capsule or muscularis of the organ to enhance peristalsis, but the parenchyma of each viscus receives a direct stimulus for increased absorption and secretion.  This is again administering a natural tonic for the massage of a viscus enhances its function and drainage.  Visceral stimulation and visceral drainage must be complements and compensatories of each other; (c) in performing massage of the plexus aorticus abdominalis, the voluntary abdominal muscles are invigorated in function and usefulness.  The active contraction and relaxation of the abdominal muscles on the viscera is a necessity for their normal function (rhythm, absorption, secretion) and support, e. g., splanchnoptotics possess relaxed abdominal walls and consequent distalward movements of viscera and elongated mesenteries - resulting in disturbed, compromised, visceral peristalsis, absorption and secretion as constipation, indigestion and neurasthenia.  Every organ has its rhythm.  In the rhythm or peristalsis of an organ undoubtedly lies the physiologic secret of correlated secretion and absorption.  Hence one of the essential duties of a physician is to aid in maintaining a normal visceral rhythm.  In conditions of acute inflammation or irritation of viscera, the abnormally active rhythm is best treated by anatomic (quietude of voluntary muscles) and physiologic rest (prohibition or control of fluid and foods).  In conditions of defective rhythm of organs as in constipation, splanchmoptosia, the best means to stimulate normal rhythm is systematic abdominal massage and vigorous visceral drainage.  A rational method to stimulate visceral rhythm is to administer coarse foods (cereals and vegetables) that leaves a large fecal residue which irritates the intestines into vigorous peristalsis or rhythm.

Fig. 7. This illustration is from a dissection made under alcohol.  It is a drawing from a subject possessing a typical large abdominal brain with the ureter, bladder and urethra dilated into a single channel without sphincters intact. 1 and 2, abdominal brain; 3 and 4, renal plexuses; 5, plexus adrenalis; 6 and 7, the two vagi; 8 and 9, the three splanchnics on each side; 10, two spermatic ganglia; 11 inferior mesenteric ganglia; 12 and 13 lumbar lateral chain of ganglia; 14 and 15, dilated ureters wrapped by nerve plexuses; 16 arterio-ureteral crossing; 17, hypograstic plexuses ; 18, and 19, lateral chain of sacred ganglia; A and B, Patulous ureteral orifices.  The Plexus aorticus extends from the abdominal brain (1 and 2) to the aortic bifurcation, whence the Plexus interiliacus (hypogastricus) begins and extends to the Pelvic brain.  I consider the Plexus Aorticus in this subject as a typical one.


Fig. 8. This illustration represents a typical aortic plexus, which I dissected under alcohol from a specimen taken from a subject of about fifty years of age. 1 and 2 abdominal brain lying at the foot of the great abdominal visceral arteries.  P. 0. S. ganglia located at the other visceral arteries.  HP, represents the fenestrated interiliac nerve disc.