eleventh Rack-bone of the Back are seventeen in number, and so many from thence downwards.
But let us return to the Muscles of the Chest serving for respiration. First, you must know that these Muscles are fourscore and nine, that is, on each-side forty four, alike in strength, thickness, fire, and action; and one besides in the midst which they call the Diaphragma, or Midriffe. Of these forty four, there are twenty two which dilate the Chest in drawing in the breath; that is, the Subclavius, the Dentatus, or Serratus major in the opinion of some, both the Rhomboides or Ser∣rati postici; the oblique ascendent of the lower Belly, the eleven Intercostales, and the six Inter∣cartilaginei externi. On the contrary, as many contract the Breast in expiration; to wit, the Sa∣cro-lumbus, the oblique descendent, the Right and Transverse of the lower Belly, the inner Trian∣gular, the six Intercartilaginei, and the eleven inner Intercostales. Of these twenty two dilating the Chest, the first from the site is called the Subclavius, for it descends obliquely from the inner and fore-part of the Clavicula or Coller-bone, into the Gristle of the first Rib, even to the Sternon, and dilates it. The second is the Serratus major, the greater Saw-muscle arising according to the opini∣on of some from the whole basis of the Shoulder-blade on the inside, and it is transversly inserted into the nine upper Ribs, producing certain toothed or Saw-like processes, running further to the Bones of the Rib, than to the Spaces between them, or Intercostal Muscles, whereupon it hath the name of the Saw-muscle; yet some have referred this Muscle to them of the Shoulder-blade. The third descends from the three lower Spines of the Neck, and the first of the Back, by means of a membranous and most thin ligament, into the three or four upper-Ribs, running further into their Spaces or Intercostal-Muscles, than into the Ribs themselves, whereupon it is called Serra∣tus posterior & superior, that is, the hinder and upper Saw-muscle. The fourth in like manner ascends by means of a membranous and thin ligament from the three upper Spines of the Loins, and the two last of the Chest, or Back, into three or four of the lower, or last of the Bastard-ribs, sent forth further into them or their Bones, than into the Intercostal-muscles possessing the spaces between them, wherefore it is called Serratus posterior & inferior, the hinder and lower Saw-muscle. More∣over these two last Muscles have been called by a common name from their figure the Rhomboides, that is, the square-muscles. The fift which we said was the Ascendent of the Epigrastrium, hath al∣ready been sufficiently described in his place. The eleven Intercostales externi, or external Inter∣costal-muscles descend obliquely from the back-part of the lower-side of the upper-Rib, into the fore-part of the upper-side of the Rib lying next under, after a quite contrary manner to the six Intercartilaginei, who having like original and insertion amongst the Gristles, as the Intercostal amongst the Ribs, descend obliquely from the fore-part backwards. And thus much of the Mu∣scles dilating the Chest in inspiration.
But the first, of the other Muscles, being as many in number, which contract the Chest in ex∣piration, arising from the Holy-bone, and the oblique processes of the Loins, ascends (firmly and confusedly adhering with the Musculus sacer, or holy Muscle, which we shall describe hereafter) to the roots of the twelve Ribs, imparting in the ascent a small tendon to each of them, by which it draws these Ribs towards the transverse processes; and by reason of its Original it is called Sa∣crolumbus, that is, the Holy-loin-muscle.
The second, third, and fourth, which we said were the oblique descendent, right, and transverse of the Epigastrium, have been formerly described in their place.
But, by the way, you must note, that these three Muscles of the Epigastrium, help expiration ra∣ther by accident, than of themselves, to wit, by driving back the Midriff towards the Lungs by the entrails, which also they force upwards, by drawing the parts into which they are inserted to∣wards their Original. The fift which we call the Triangulus, or Triangular, may be called the com∣pressor of the Gristles, which proceeding from the inner sides of the Sternon, goes to all the gristles of the true Ribs; this is more apparent under the Sternon in Beasts, than in Men, though it be not very obscure in them neither. For the internal Intercostal-muscles, in my judgment, they arise from the lower sides of the upper-rib, and descending obliquely from the fore-part backwards, are inserted into the upper-side of the rib next under it; so that they may follow the produ∣ction of the fibers of the external Intercartilaginei; as the six Internal Intercartilaginei, follow the site of the external Intercostal, proceeding from behind forwards; wherefore as well the Inter∣costal, as the Intercartilaginei, every where intersect each other, after the similitude of the letter X. I know, some have written that the Internal-muscles (whether Intercostal or Intercartila∣ginei) ascend from the upper-side of the lower rib, forwards and backwards.
But if this were true, it would follow, that these Muscles admitted their Nerves in their Tail, and not in their Head, seeing the Nerve alwayes goes under the Rib, and not above it.
The last Muscle of the Chest, that is, the Diaphragma, or Midriffe, is sufficiently described be∣fore; wherefore it remains, we describe the Muscles of the Loins. These are six in number, on each side three, equal in thickness, strength and situation; one of these bends, and the other two extend the Loins; it is called by reason of the figure, the Triangulus, or Triangular which bends the loins; it ascends from a great part of the hind-side of the hanch-bone into the transverse pro∣cesses of the loins, and the last of the chest, on the inside, for which cause it is made of fibers, short, long and indifferent, answering to the nearness or distance of the said processes. The first of the ex∣tenders is called Semispinatus, because even to the middle of its body it takes the original from the Spines of the Holy-bones and Loins, this with its oblique fibers ascends from all the said Spines to the transverse processes, as well of the loins as chest. The other is called Sacer, the Holy-muscle, be∣cause it takes its orignial from the Holy-bone, or the sides thereof; it ascends with its oblique fibers to the Spines of the Loins, and of the eleven lower Rack-bones of the Chest.