CHAP. XXV. A Description of the Intercostal Nerve.

AFter the unfolding of the Nerve reaching forth to the Praecordia and the Ven∣tricle, we are led by the series or order of the inward parts to the describing a Nerve akin to this, and which reaches forth its branches to the furthermost Province, to wit, to all the Viscera or Inwards of the lower Belly contained below the Ventricle. This is commonly called the Intercostal, because that going near the roots of the Ribs, it receives in every one of their Interstices a branch from the spinal Marrow. Its beginning is not yet sufficiently detected; for by most Anatomists it is wrongfully taken for a branch of the wandring pair, though indeed the wandring and the inter∣costal pair do communicate among themselves by branches sent forth one to the other; yet as to both their beginnings, Trunks and wandrings up and down, they are plainly distinguished. If that this latter Conjugation, being denied the title of a peculiar nerve, ought to confess it self of another stock, certainly it owes nothing to the wandring pair, but should borrow its original from the Nerves of the fifth and sixth pairs; for two or three shoots being sent back from those nerves going out to∣wards the Eyes and Face, go into the same stock or Trunk, which is the Trunk of the intercostal nerve, as we have intimated before.

The intercostal Nerve being constituted after that manner, and going out of the Skull at a proper hole, presently contains the Ganglioform infolding, near to ano∣ther the like infolding of the wandring pair; into which two nervous Processes are carried from the last pair within the Skull, or the first Vertebral. From that infold∣ing one shoot is sent forth into the Sphincter of the Throat, and another noted one into the Ganglioform infolding of the wandring pair. Then this nerve descending towards the Vertebrae, hath in the middle of the Neck another far greater infolding, into which an ample nerve, from the neighbouring Vertebral pair, is inserted; but from the same many nerves, which respect the Praecordia, are distributed on every side: For two or three shoots are sent forth into the nerve of the Diaphragma, and one shoot into the returning nerve; besides, numerous fibres and shoots are carried both into the returning nerve, and towards the Trachea, which are inserted into its Coats, and into those of the Oesophagus, and into the blood-carrying Vessels. Fur∣ther, one branch descends into the Trunk of the wandring pair, and two noted nerves into the Cardiack infolding; then a little lower another nerve by it self, proceeding out of the intercostal Trunk, is inserted also into the Cardiack infolding: which noted branches sent down on both sides from the intercostal nerve, for that they joyn Page  158 together with others derived from either Trunk of the wandring pair, make the Cardiack infolding it self. But these Cardiack branches from the intercostal nerve, as also the Cervical infolding, or that in the hinder part of the Neck, whence they proceed, are peculiar to men, and are wholly wanting in brute beasts.

The intercostal Trunk descends from the cervical infolding towards the chanel-bone, where being about to enter the cavity of the Breast, it falls upon the axillary Artery, as it were in right Angles, and strains or binds it; from whence it is drown∣ed or hidden in the Thorax near the roots of the first and second Ribs; and there re∣ceiving three or four branches from the Vertebral nerves next to those uppermost, constitutes another infolding, which is commonly called the Intercostal infolding. The uppermost of these Vertebral nerves coming to this infolding in its journey binds the Vertebral Artery, and almost compasses it about. In Brutes by this nerve which comes upon the Vertebral Artery, the intercostal infolding communicates with the root of the nerve of the Diaphragma, and not by any other means, unless by small fibres sent forth from the lower part of the infolding into the Vertebral nerves. Fur∣ther, in Brutes a noted branch is carried from this infolding into the Trunk of the wandring pair. But in Man the intercostal Trunk passes through the cavity of the Thorax without any communication had with the other parts; unless that from hence in its whole descent, running near the roots of the Ribs, it admits in every one of their interspaces, and from thence even to the Os sacrum from between the knots of the Vertebrae, a Vertebral branch.

The intercostal pair sends forth a noted branch on either side, where having gone through the cavity of the Thorax or Breast, it comes over against the bottom of the Ventricle, which tending towards the Mesentery, constitutes the chief infoldings of it. But there are seven Mesenterick infoldings, viz. five great superior, and two less inferior: out of all which, numerous shoots and fibres are sent forth together into the parts which they respect, and into the neighbouring infoldings. The Mesenterick nerves, which are carried into these infoldings, and the infoldings themselves, and also the fibres and shoots, which flow out from them on every side, like rays of light, are disposed according to the following manner both in Man and in the more perfect Brutes.

The Mesenterick branch therefore in the left side going from the intercostal Nerve, and bending downwards, is parted into two noted shoots: the greater of these bend∣ing back upwards towards the Stomach, diffuseth it self presently into an infolding, as a narrow rivulet into a spacious Pool. From this infolding numerous fibres and shoots go forth as it were in four bands. The first of these, and which is the greatest bundle of its fibres, being carried into the Ventricle, is bestowed partly in the bot∣tom of it, and partly these fibres are met, and ingraffed with others sent from the-Stomachical branch. The other maniple or band of nervous Fibres goes forth from this infolding to the Spleen, where the nerves accompanying the sanguiferous Vessels, and variously binding them about, are dispersed into the more inward frame or sub∣stance of the Spleen; yet out of which going towards the Spleen, some shoots follow∣ing the short Vessels, are carried into the Stomach. The third Company of nervous Fibres is inserted between this infolding and the Hepatick or that belonging to the Li∣ver, placed in the right side over against it. Lastly, the fourth Conjugation of Fibres knits together this and the greatest infolding of the Mesentery lying under it.

The lower shoot of the Mesenterick branch, which is on the left side, increases into an infolding, to which the next Vertebral branch, destinated to the intercostal Nerve, is carried. From this infolding the chief bundle of nervous Fibres is carried into the left Kidney, and before the Fibres enter the Reins, they bind and variously compass about the emulgent Vessels. Further, between this infolding and the great∣est of the Mesentery many Fibres are stretched out; from hence also many shoots are distributed into the atrabilary Chest, or the Receptacle of the Spleens excrements.

In the right side the Mesenterick branch being sent from the intercostal Trunk, and being in like manner twofold, contains in its upper shoot the Hepatick infolding; out of which the greatest bundle of nervous Fibres is carried towards the Liver; nu∣merous shoots of which accompanying the blood-carrying Vessels, greatly beset, and as it were cloath with a little net the Trunk of the Hepatick Artery: which fibres and shoots, being carried higher, are distributed into the Liver, the Gall-chest or bag, the passage of the Gall, the Pylorus, and the Pancreas. Further, many Fibres, which are of this Conjugation, meet with Fibres sent from either Stomachical nerve, and Page  159 are ingraffed into them. Another handful of nervous Fibres is stretched out between this infolding and the opposite infolding belonging to the Spleen, and another be∣tween this and the greatest infolding of the Mesentery; yea, there is some communi∣cation had between this and that belonging to the Kidney lying under the same side by a large shoot sent down.

The lower shoot of the right Mesenterick branch, like as it is in the opposite side, contains a sufficiently noted infolding nigh the atrabilary Chest; to which presently the intercostal Nerve imparts its Vertebral branch received below. From this in∣folding the chief bundle of nervous Fibres destinated to the Reins, embraces the blood-carrying Vessels in like manner as in the opposite side; also many fibres and shoots are stretched out from this infolding to those near, viz. the Hepatick and the greatest of the Mesentery; yea, certain Fibres are dispersed from the same into the atrabilary Chest.

After this manner either Mesenterick branch being carried from the Intercostal pair, and being presently twofold, immediately constitutes two infoldings in either side. In the midst of these the greatest infolding of all stands like the Sun in the midst of the Planets; from which numerous shoots and fibres are dispersed into all the parts of the Mesentery; which indeed following the blood-carrying Vessels in their whole process, climb over and bind about the same. Moreover, between this infolding and every one of the four aforesaid is produced a peculiar little bundle of Fibres. Besides, in the female Sex, from hence some shoots are carried into the Glandula's of the Womb, commonly called the Stones. But from the Mesenterick branches, which constitute the former infoldings, no noted branches, but only little shoots, are sent into this infolding. Yea the chief Nerve which is inserted to this, and seems to be the primary for the conveying of plenty of Spirits into it, and a broad way, is carried from a certain small infolding far lower nigh the straight Intestine; which infolding, together with the other neighbouring one, that we call the lesser infoldings of the Mesentery, shall be described presently. In the mean time, that we may proceed to them in order, we will follow the passage of the intercostal Nerve.

Below the Mesenterick branches, from which the aforesaid superior infoldings are constituted, the intercostal Trunk descends between the Muscles of the Loyns, and bestows every Vertebral branch, admitted in its descent, upon some internal parts.

For the Vertebral branch brought to the intercostal Trunk nigh both Kidneys, is carried into the Womens Testicles, then some following into the Ureters. From the Region of the twenty seventh Vertebra one Vertebral branch and two others, going from the intercostal Trunk, tend towards the straight Intestine, and there they meet with three pairs sent from the other side; all which being united, constitute the in∣folding, which is the lowest of the Abdomen. From this infolding a noted Nerve, being carried upwards, is brought into the greatest infolding of the Mesentery, which in its journey receives one and then another shoot sent down on both sides from the intercostal Nerve; and there, near its bounds, distributes some shoots into the Glan∣dula's of the Womb.

But from the lowest aforesaid Infolding, a Nerve going towards the upper Infold∣ings, about the space of an inch, constitutes another lesser infolding in the neighbour∣hood; out of which one Nerve tends upwards, and another opposite straight down∣wards. The former of these is carried into the greatest infolding of the Mesentery, and in its whole passage stretches under the straight Intestine, and part of the Colon, and inserts into them many small shoots. But the other Nerve descending from this infolding towards the Anus under the inferior part of the straight Intestine, imparts to it also frequent shoots; so that this infolding, the least of all those which are with∣in the Abdomen, seems to be constituted for the sake of this Nerve only, to wit, which lying under the straight Intestine and part of the Colon, is inserted into the greatest infolding of the Mesentery.

From the lowest neighbouring Infolding, to which this least owes its original, two Nerves going out, and being sent down into the Pelvis, cause there two infoldings, viz. one in either side, in which the Nerves coming from the Os sacrum, and ingraf∣fed with the former, meet; from which also the Nerves distributed into the adjacent parts, serve unto the several Excretions, viz. of the Urine, Dung, and Seed made in that place: for two Nerves enter into the end of the straight Intestine, and as many into the Womb or Prostates; but one, and that a noted one, is carried into the Bladder.

Page  160But that we may return to the Intercostal pair, after either Trunk of it had sent forth three branches, out of which the aforesaid lower infoldings of the Abdomen are mediately or immediately made, it descends straight towards the Os sacrum, and in its journey sends forth yet one or two branches into the Ureters: but as soon as it is come to the beginning of the Os sacrum, both nerves mutually inclining themselves to one another, are demerged within the bending of the same bone, and there nigh its declining, and then in its descent, they seem to be knit together upon it by two or three processes; and so at length either nerve ends in very small fibres, which are distributed into the Sphincter of the Anus. But sometimes either nerve joyn together into a round infolding nigh one transverse process, out of which single infolding the like very small Fibres are produced. Further, many others from the last Vertebral Nerve meet with, and are ingraffed with these Fibres from the intercostal pair in∣serted into the Anus.