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THE FOURTH TABLE.
Fig. 1.
REPRESENTS a Portion of the Cuticula or Scarf-skin, rais'd from the Back of the Hand, and viewed with a Microscope.
A A, The Perforations or Pores, whereby the Sweat is discharged.
B B, The Indentures or Furrows.
C C, The Bladder like Protuberances; both these arise from the Inequallity of the Papillary Surface of the Skin it self.
D D, The Hairs which break forth through the Cuticula.
E E, The Asperities or Filaments, by which the Cuticula is fastned to the True Skin.
With the Assistance of the Microscope, the Cuticula appears composed of divers Strata or Beds of Scales, fastned to the Papillary Surface of the Skin; and are so intangled with each other, as that they appear a con∣tinued Pellicle or Membrane when rais'd from the True Skin, whether by the Application of Blister-Plasters in Living People, or Scalding Water, Hot Irons, or the like, in Dead Bodies: According to the Number of these Strata or Beds of Scales, the Skin appears to be more, or less Fair, and the Person is commonly said to have a thicker or thinner Skin; tho' ve∣ry frequently the Jaundice and other Diseases give it an ill Tincture. The Cuticula like the True Skin is not Uniform, in divers Parts of it the Number of its Scales and their Strata exceed those of others; on the Lips not above two Strata appear; on other parts more, seldom less; in the Bottoms of the Feet of those who walk much, and the Palms of the Hands of Laborious Mechanicks, these Strata are not only very nu∣merous, but each Scale is thickned. If you Macerate the Cuticle in Water, after some days, its Strata of Scales will appear, and you may divide it in∣to Two, sometimes Three, or Four Pellicles; the like Division of it may be also observ'd in Vesicatories or Blisters rais'd on Living Persons.
Fig. 2.
A Portion of the Cuticula rais'd from the Bottom of the Foot, and view'd with the same Microscope as the former; where its remarkable Thickness appears.
Fig. 3.
A Portion of the Cuticula rais'd from the Back; in which the Inden∣tures, Furrows, &c. agree with those of Figure the 1st. The Surface of the True Skin of that Part being exactly agreeable with that of the other; but at the Extremities of the Fingers, and Thumbs, the Cuticle is variously wreathed and contorted, conformable to the subjacent Papillary Protu∣berances of the True Skin, as appears in the following Figure.
Fig. 4.
The Upper and Inner Side of the Thumb drawn likewise by the Assi∣stance of the Microscope.
A, From the Point arise
B B, Two Lines, of a Circular Disposition;
C C, Others which form Triangles.
D, Other Lines variously contorted or winding.
The Cuticle being remov'd, the Cutis or Skin it self appears.
Fig. 5.
A Portion of the Skin of the Arm, as it appears on its External Sur∣face to the naked Eye.
Fig. 6.
The External Surface of the Skin, when view'd with a Microscope; where its Internal Structure or Rete of Blood Vessels are also exprest.
A A, The Papillae Pyramidales; made up of divers Pyramidal Round∣ish Glands, in whose Composition the Nerves have a considerable Share.
B B, The Capillaments of the little Aqueous Vessels placed between the Papillae according to Bidloo. I must confess notwithstanding all the Diligence I could yet use in examining this Part with the Micro∣scope, or otherwise, I have hitherto doubted of the Existence of these Aqueous Vessels, between the Cuticula and Cutis; in which some have placed the Seat of that Tawny Tincture of the Aegyptians, and that Black one of the Aethiopians.
C C, The Sudoriferous Glands, which compose the Papillae.
D D, The Sweat Vessels or Excretory-ducts arising from the last mentioned Glands.
E E, The Hairs arising near the Pores of the Sweat Vessels: Be∣sides these Vessels, the Skin is furnished with Arteries, Veins, Nerves, and Lympheducts; the Trunks of the Two former are well exprest in this Figure F F: Hence it appears the Skin can no more be esteem'd a Similar or Simple Part, than any of those call'd Dissimular or Compoun∣ded Parts. Nor is there any Part of the whole Animal Oeconomy, that can be justly esteem'd Simple or not Compounded; even the Blood Ves∣sels, Nerves, and Lympheducts are Compounded Parts, as shall be else where demonstrated. Besides the Pyramidal Sudoriferous Glands, which compose the Papillae Cutis, there are other Sudoriferous Glands placed on the Internal Surface of the Skin; the most considerable of these we find in the Axillae, where they are sometimes call'd Axillares, but more properly Miliares, from their Figure; the Axillary Glands lying un∣derneath these Sudoriferous ones; they receiving the Lympha, brought into them by the Lympheducts springing from the whole Arm, do dis∣charge it again into the Exporting Lympheducts in its Way to the Tho∣racick Duct. There are other Sudoriferous Glands, tho' not so evident to the naked Eye, under the Skin of the Fingers, Inguina, and behind the Ears: The Hairy-scalp, Skin of the Forehead, Palms of the Hands, and Soles of the Feet are also furnished with these Glands; wherefore we shall not distinguish them with the Names of the Places of their Si∣tuation, but choose to give them a more general Denomination, either as to their Office, as Glandulae Sudoriferae, or Figure, as Miliares. In the Skin also are placed those Bodies whence the Hairs arise; these, by some are also esteem'd Glands, and call'd Piliferae: These Piliferous Bo∣dies or Glands, are furnished at their Roots with Importing and Exporting Blood Vessels, Nerves, &c. the Hairs being as it were their Excretory Ducts with this Difference from those of other Parts, viz. They receiving their separated Juyce immediatly from the Pores in the Extremities of the Blood Vessels; whereas the Hairs, as we conceive, have their Radi∣cal Moisture transmitted to them by the Mediation of a Spongious Body which absorbs it from the circumjacent Parts: Hence it is that the Hairs grow in dead Bodies, when the Natural Motions of the Fluids cease. The Hair between the Light, and naked Eye, appears pellucid; but if viewed with a Microscope in that Position, it appears Spongy, or not unlike the Internal Part of a Cane: It seems to be compos'd of horny globular Particles variously joyn'd together, and colour'd, where it hath Plenty of Moisture, it is commonly Pendulous; if more Dry, it is Curl'd.
Fig. 7, 8.
Two of the Hairs of the Head figur'd with a Microscope:
A, Its spongious Body compos'd of horny globular Particles.
B B B, Its straight and transverse Stalks, which joyn its Globules to∣gether.
C C C, The woolly or downy Part of the Hair, which descends from above, and stands obliquely downwards; whence it happens, when the Ends of the Hairs are not placed in their right Position, the Hairs are apt to intangle in Combing, as it do's in those Periwigs made of what they call Combings.
D D, The Top of the Hair divided:
E, Its Middle Part:
F, Its Root arising from the Piliferous Body, placed within the Skin.
G, A Portion of the Cuticle, which commonly sticks to the Hair when extracted.
Fig. 9.
The Branches, which sometimes appear on the Top of the Hair by a Microscope.
Fig. 10, 11, 12.
The different Thickness of the Hairs of divers Parts of the Body, when view'd with the same Microscope. Figure the Tenth, that of the Groin; the Eleventh, that of the Nostrils; the Twelfth Figure repre∣sents the Hairs of the Eyelids.
Immediatly under the Skin is placed the Fat in Humane Bodies; nor is it found in all Parts alike; on the Forehead it is very little, under the Hairy Scalp less, except its Hinder Part, on the Eyelids and Penis none, nor on the Muscu••us Quadratus Colli.
Fig. 13.
A Portion of the Fat of the Abdomen.
A A, Its External Membrane.
B B, Its Internal Membrane.
C C, The Globules of the Fat with their Blood Vessels passing to them, whence their oyly Contents are deriv'd.
- 1. The Integument or Covering of the Globules of Fat rais'd.
- 2. The Globules of Fat themselves.
- 3. Some of the Globules divided from the rest; in which the Breaking off of their Membranes, and Blood Vessels, are exprest: Hence it appears, that the Fat is a Congeries or Heap of Membranous Cells, which in the Microscope appear distended with Oyl: If the Existence of those Ductus Adiposi could be demonstrated, as Bidloo intimates at C C in the last describ'd Figure, I should incline to think of another Office of them intended in Nature, than what Malpigbius has assigned them, viz. To convey the oily Contents of the Adipose Cells to some neighbouring Interstices, whether of Muscles, or other Parts, that are on Occasion mov'd, or slide on each other; or into some remarkable Ca∣vity, as into that of the Abdomen, &c. where it meets with a Mucilage se∣parated by the Mucilaginous Glands placed in the neighbouring Mem∣branes, and serves to make up a Composition to Lubricate the Parts ac∣cording to Doctor Havers's Osteologia Nova, Pag. 209.
Fig. 14.
The Outside of the last Common Integument of the whole Body, call'd the Common Membrane of the Muscles; some divide this into Two Membranes, and distinguish them by the Names of Carnosa and Communis Musculorum; which we look on to be altogether needless as may ap∣pear by the following Description.
Fig. 15.
The Inside of the Membrane last described: The rise of this Membrane is commonly said to be from the Spines of the Vertebrae of the Back, because as I suppose that is the most stable Part to which it's Connected: It is co∣extended with the Skin it self, as appears in most Parts, and has its Cor∣responding Foramina for the Eyes, Nostrils, Ears, Mouth, Anus, and Pudendum: As to its Intimate Structure, I have always met with con∣curring Experiments and Observations, of its being an Extensible Bo∣dy, compos'd of divers Strata or Membranes, framing Cells, which have divers lesser Cells or Loculi within them; and in divers Parts, where the Loosness of the Skin it self would admit, those lesser Cells or Loculi, are fill'd with Oil, and are call'd Fat; but in other Parts where either the Hardness of the subjacent Bone, when the Skin is extended, as on the Top of the Skull, or the repeated quick Motions, as of the Eye∣lids, or the Structure of the Part, as of the Penis; these Membranous Loculi are not so extended with Oil, as to make an Appearance of Fat; whence it is we find this Membrane much thicker in those Parts last mentioned, than in others; and on the contrary, thinner and fewer Strata of Laminae, where its Cells are partly possest with Fat. This Common Membrane is furnished with Vessels of all sorts; nor is it con∣fin'd to the Surface of the Muscles only, but insinuates in their Intersti∣tia, and helps to compose their Coverings; whence it happens that by blowing into the divided Strata of the Cells of this Membrane, the whole Body of the Animal is Tumified; which is commonly practised by Butchers, especially in dressing their Veal.
The common Integuments of the whole Body being demonstrated, we proceed to those particularly belonging to the Head; nor shall we omit speaking again of these hereafter, where any thing in their par∣ticular Parts occurs to our Observation or Memory, which the suc∣ceeding Figures may help us to explain.