These Hairs are by some thought to have for their nourishment a proportionable quantity of that juice of which they are generated , continually ministred unto them . Others think that the Hairs being hollow and porous are nourished as the Feathers of Fowl are , and that is by bloud ; for if one pull off a Feather from a young Bird that is unfledged , a pretty deal of its stem will appear bloudy . But though we should grant that the matter of their nourishment were made of bloud , yet certainly it must be very much altered and degenerate from its own nature , before it can be adapted to the hair , seeing the hair of a Man's head ( for example ) grows not onely in living persons , whose bloud runs briskly in their Arteries and Veins , whereby it is kept from corruption , but also in the dead , in whom the whole mass of bloud is devoid of all nutritive power , as has been often observed in bodies preserved unburied . But whatsoever the humour be that nourishes them , it is thrust through the skin by the pores thereof , the action and heat of the body assisting thereunto , where the purer part of it enters the roots of the hair , but the more earthy not being able to enter such almost unperceivable pores , is driven out amongst the hair where it becomes dust ; which dust is that that is brought forth with the Curry-combe when a Horse is drest . From hence then it is , that a Horse , though he be never so well dressed one morning , and never so clean kept till the next , he shall notwithstanding be as full of dust as he was the morning before ; for the cleaner the skin of a Horse is kept , the more open are its pores to transmit a more plentifull nourishment to the hair , whence also there is a greater collection of this excrementitious dust .

And hence may be gathered a reason of the shedding of the hair , which is observed to happen in many Horses that have ill keeping , such as your Cart-horses that seldom have any labour bestowed upon them , for want of which dressing , to remove the dust which lieth upon the mouths of the pores or at the roots of the hairs , the passages , through which the juice should come that nourishes the hair , are obstructed or stopped , and so like dead Leaves from a Tree in Autumn they drop off , or as untimely Fruit falls before the season of the year requireth it .

As for the Colours of the hairs , they are various , according as is the humour which doth predominate in the body : for such as the humour is which is driven forth towards the skin for their nourishment , such will the colour of the hair be . As for Instance :

If the cholerick humour doth most predominate , then are the hairs of a black , a Sorrel or a Chestnut colour ; If bloud most predominate , then will the Horse be a bright Bay or Roan ; If flegme , then the Horse will be of a milk-white or yellow-dun ; If melancholy , then will the Horse be of an Iron-gray or Mouse-dun . Thus much for the colour of the hairs , next I come to the use of them .

The use of the hairs is , first , to cover the skin ; secondly , to defend it ; thirdly , to be an ornament to it ; and lastly , as I have before shewed , to suck up that excrementitious superfluous juice which through the pores of the skin is sent from all parts of the body to them .

THE Hide on which the hairs already spoken of do grow , consists of two Skins , the outer of which is called the Scarf-skin , serving to defend the Body from outward Injuries , and for that intent is of it self Insensible , that it may the better indure the violence of the weather , or other harms which many times happen to it . And for that cause , Nature hath so ordered it , that if at any time it happeneth to be rubb'd off , as often it is by an ill Saddle , and many other ways , it groweth again without a scar or blemish , provided the Parts under it ( as particularly the true Skin ) be not also violated ; for they being spermatical Parts , or made of Seed , cannot easily be restored , which is the reason that most Wounds will not heal up without a scar . Now this Scarf-skin having its matter ( of which it is made ) from the true Skin and the Vessels that terminate in it , which are of all sorts , both Veins , Arteries and Nerves , none of which reach any farther than the true Skin , it is apparent that this Skin is without sense , it being their office alone to communicate both life , sense and motion to all parts of the Body . And that this Skin is void of sense , may be seen by the cutting of it ; as thus , If you cut onely through this Skin , when you go to Rowel a Horse , you shall not find the Horse move for it , neither will it bleed ; but if you cut so far as to touch the true Skin under it , you will find him both stir and bleed , for then you touch the little threads of the Vessels , and by violating them , you cause the Horse to feel pain , and also bloud to issue forth .

The use of this Skin , besides being a covering to the whole Body , is to cover the mouths of those small hairy Vessels already spoken of , that the bloud , spirits , or other ichorous or watery Matter do not issue from them , which otherwise they would . Yet its Pores are so large as to permit the vapourous moisture that is thrust out of all parts of the Body to it , to pass through them , either in the form of sweat , or by insensible transpiration . These Pores being many times obstructed or constringed by a sudden cold taken after hard riding , by giving the Horse cold Water too soon after it , or by washing him too high in cold Water when he is hot , the Vapours are thereby hindered from coming forth , and so are detained between the two Skins , and there generate evill Distempers , or at least fall from thence into the Limbs , and there cause Inflammations and breakings out , which we call Grease in the heels or Scratchets .

UNder this Scarf , lieth the true Skin , which the Latines call Cutis . It s substance , as I have before shewed , is said to be spermatical , such as being once lost , cannot be restored as formerly it was , but is reunited by a cicatrice or scar , that is bred of the dried and constringed flesh under it ; which is the reason no hairs will grow upon that part of the Skin where the scar is , because it is callous and destitute of Pores in which they should grow . This Skin doth encompass the whole Body as well as the Scarf , and hath the same passages for the receiving in , and letting out , for the ease and relief of the Body , as that hath .

It hath for its nourishment , life , and sense , Vessels of all sorts , Veins , Arteries and Nerves , divaricated and branched through it in the smallest hair-like threads , all which terminate in it , none of them being inserted into the Cuticle .

As for its colour , it varieth as do the humours in the Body ; for that humour which most abounds , coloureth it with its proper respective colour ; as for example , If bloud most abound , then is it most red ; if choler do most predominate , then is it yellowish ; and so for the other humours .

It s use is principally to invest and defend the Body , as I have said before of the Scarf-skin : for as that keeps it from the violent impression of either excessive heat , or cold ; so doth this Skin restrain , and , as it were , wall in ( as in a Castle ) all the spirits and natural heat , which would otherwise in hot weather , or in violent exercise be so fast spent , that they would leave the vital parts destitute , which would occasion the loss of your Beast . But though Nature has made this provision to hinder the dissipation of the spirits , yet has she framed the Skin ( as well as the Scarf-skin ) full of small Pores , through which upon violent exercise do issue in great plenty hot and moist vapours , which are that we call sweat ; yea though the Beast be at rest , if the Air be any whit mild or temperate , warm steams are continually a passing through them by insensible transpiration .

It 's also as serviceable in cold weather , for then the more fiercely it is besieged by the cold , the narrower do the aforesaid Pores purse up themselves , whereby the internal heat is detained within , and the external cold kept out .

NEXT to the true Skin , lieth the fleshy Pannicle , called membrana Carnosa , or panniculus carnosus , because in most parts of the Body , it comes near to the nature of flesh , and is truly muscular .

In Man this Membrane is said to lie under the Fat , though some very curious Anatomists deny that Man has any such Membrane at all , save in the Forehead ; and of this opinion is Dr. Glisson . I will not intermeddle in that Controversie , as being not proper for me ; but in Horses it lies immediately under the Skin , above the Fat , and is more like to a Muscle than a Membrane . In fleying off the Skin , you must be very carefull and curious , or else you will take this Pannicle off along with it , it is so closely knit to it by Fibres and innumerable Vessels that go between . It is of the same extent and figure as the true Skin , investing the whole Body as that does ; but in some Parts it is almost wholly fleshy , and in others altogether membranous .

It has Vessels of all sorts as the Skin has , for before they can reach the Skin , they must pierce through this Membrane ; and as they pass through , they send forth many small twigs into it , both Veins , Arteries and Nerves , but especially Nerves to assist its motion , whence it is by some called the nervous Membrane .

The use of it is chiefly to serve for a Muscle to move the Skin , whereby the Beast shakes off the Flies , or any other thing that offends him . It serves also to defend the neighbouring Parts , and to strengthen in their passage the Vessels which are disseminated into the true Skin . It also hinders the Fat from being melted and spent by the continual motion of the Muscles . And lastly , it helpeth to heal or close up the Skin when it is cut or otherwise hurt ; for the Skin being a spermatick Part cannot be bred anew , and therefore this fleshy Membrane helps to glew as it were the sides of it together again , growing into one body with it , and making what we call a Scar.

But here let none so far misunderstand me as to think that either an Arm or Leg can be either stretcht forth or drawn back by the help of one Muscle alone ; but as to either of the before mentioned Limbs there are several parts belonging , so do the distinct Muscles of every part perform ( at the same time ) the offices aforesaid .

Neither can this voluntary motion be performed without the help of a Sinew or Nerve , by which the Spirits are brought from the Brain which give the Muscles their moving faculty .

Now there are other motions of the Body which are not performed by the Muscles , such as is ( according to some ) the pulsation of the Heart and Arteries , the peristaltick motion of the Stomach and Guts , of the passage of the Gall , and of the Ureters , and several other Parts which have their continual motions whether the Horse be sleeping or waking , and will perform their several motions as well in Men as Beasts , whether we will or not . Wherefore these are called not Voluntary , or Natural .

I shall in the next place shew what parts the Muscles are compounded of , and those are agreed upon by all Authours of Anatomy to be these .

A Muscle being an organical Part is composed of Nerves , Flesh , Fibres , Veins and Arteries , all covered or invested with a proper Coat or Skin . It is called organical , because it is the instrument or organ of an action , to wit , motion . And that it is also dissimilar , the several kinds of parts whereof it is made , do evidently prove . The several uses of the parts that make up a Muscle are these : The Fibres and Tendon are the immediate instruments of its action ; The Flesh properly so called filleth up the interstices or distances between the Fibres ; The Arteries by importing vital spirit and bloud do conserve the inbred heat , and help to nourish it ; The Veins do convey back to the Heart all that bloud that remains from the nourishment of the Muscle ; The Nerves convey animal Spirit to the Fibres and Tendon , whereby they are enabled for their action ; and the Membrane or Skin which incompasseth the Muscle , doth keep it together , and distinguishes one from another .

Having shewed what a Muscle is , and the several simple parts whereof it is made , I shall next shew you why it is so called . It is called mus , or musculus , by the Latins , for that it is like a fley'd Mouse , or a Fish which is called musculus ; and by some Authours it is called by the name of lacertus , from its similitude with a Creature called a Lizard . Yet there can be no one certain figure whereby to resemble it , by reason of its sundry shapes ; but that it is like a fley'd Mouse in colour , cannot be denied .

Now the Muscles being many in number have accordingly many names , which names they take from either their Figure , their Situation , or their Action , and many times from their Use ; also sometimes from their Insertion , and sometimes from their Magnitude .

And although there be such difference in the Muscles , in respect of their Figures , their Magnitude , their Situation , and the like , yet are they so united or conjoyned together through the whole Body , in so close a manner , that in many places they are hard to be separated , except at some times , when either wind , some wheyish humour or some other matter gets between them , and then many times they will gape , and are at some distance the one from the other .

Yet are they not so closely united neither , but that by a carefull and expert Dissector they may be separated , and one divided from another ; after which , to see the several parts of a Muscle severally , you must divide it also , which is on this manner .

Some divide a Muscle into two parts , which are a fleshy and a tendinous part ; Again , they divide it into other three parts , namely , the Head , the Middle and the Tail . By the Head is to be understood the beginning or original of a Muscle , which is one while ligamentous and nervous , and otherwhiles fleshy : By the Middle is that part meant which is absolutely fleshy ; and by the Tail , the Tendon , consisting of the numerous Fibres that are extended through the Muscle , and the Membrane that invests it , which grow by little and little into one body , and compose this Tendon , that is the tail of the Muscle . It is sometimes round , sometimes broad ; other times long , and otherwhiles short , thicker or slenderer according to the part it appertains to , or according to the use it is put to ; it being but necessary that those Parts which are moved most strongly or vehemently , should have thicker and stronger Tendons . Thus much for the Muscles in general .