Buckmaster's Elements of animal physiology / by John Angell.

  • Angell, John
Date:
1866
Catalogue details

Licence: Public Domain Mark

Credit: Buckmaster's Elements of animal physiology / by John Angell. Source: Wellcome Collection.

    267/384 (page 255)
    vation are formed by minute nerve loops previously referred to, projecting above the rest of the surface. The cuticle which lines their surface dips in between these rows of papillce and gives rise to the grooroed marking referred to. The papillce are most numerously distributed to the palms of the hands, the tips of the fingers, the lips, and the tongue. In the latter they have not the same regular arrangement that they have in the former. Structure of the Papillae.—When the cuticle is removed the papillce, as shown in the diagram, consist of a number of minute conical bodies. They are about I-tooth of an inch in height and I-250th of an inch in diameter. They are com- posed of a central nerve loop fibril, and of a capillary vein and artery invested externally by the basement membrane. The papillce really constitute a prolonga- tion of the true skin into the substance of the cuticle. (See F, Fig. 49.) In addition to the parts just men- tioned the papillcB of the most highly sensitive surfaces are found to contain a minute, microscopic, hard, solid, oval Fig. 50.—Dermis and body, termed the axile body, or tactile Papill.® OF Foot. corpuscle. These bodies occupy the centre of the papillae; they receive the end of the nervous fibrils, which, in some cases, pass up their centres and terminate in their axes, but in others wind round their circumference. They very much resemble the Pacinian corpuscles in their structure. Pro- fessor Huxley regards them as composed of modified 7ieurilefn7na. Their function is not well understood ; but they are supposed, as in the case of the otolithes in the ear, to render sensation more ac7ite. It has been calculated that upwards of 2,400 papillce exist in one square inch of skin on the tips of the fingers. The papillce in some parts of the skin, as on the t07igue, are not conical, but variously shaped. The Skin a Respiratory Organ.—The skin absorbs oxygen and exhales carbonic acid gas. This may be proved by confining the human body in an oiled silk bag fastened round the neck. The residual air in the bag will be found, on careful analysis, to contain less than its ordinary proportion of oxygen,