A Treatise on Anatomy, Physiology, and Hygiene (Revised Edition) by Calvin Cutter (read more books .txt) ๐
13. One of the most important distinctions between animals and plants, is the different effects of respiration. Animals consume the oxygen of the atmosphere, and give off carbonic acid; while plants take up the carbonic acid, and restore to animals the oxygen, thus affording an admirable example of the principle of compensation in nature.
14. But the decisive distinctions between animals and plants are
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Fig. 118.
Fig. 118. The hair follicle (1) is represented as imbedded in the cellular membrane, (2,) which is situated beneath the skin. 3, 3, The membranous sac, which has a narrow neck, opening externally by a contracted orifice, through which the hair (4) passes. Its internal surface is smooth, and not adherent to the hair, but separated from it by a reddish fluid. From the bottom of the sac (5) the pulp of the hair arises, and passes through the skin at 6.
717โ723. Describe the appendages of the skin. 717. Why have not hairs vitality? Where do they take their origin? Give their structure. What is represented by fig. 118?
323718. The color of the hair varies in different individuals, and is generally supposed to depend on the fluids contained in the pith. There are two causes which act in changing the hair gray. The first is, defective secretion of the coloring fluid. The second is, the canals, which convey the fluid into the hair, become obliterated. In the first instance, the hair will remain; in the second, it dies, and drops out; the cuticle of the scalp grows over the canal, which is soon obliterated, and the head becomes bald.
Observation. It is related that the hair of Marie Antoinette, Queen of France, and others, from excessive mental agitation, changed from black to gray in a single night. This is not strictly true; the secretion may be arrested, but that already deposited in the pith will require days or weeks to be removed.
719. Upon the upper part of the head, the oil-tubes open into the hair-sacs; consequently, the secretion of the oil-glands is spread over the surface of the hair, and not upon the cuticle. This is the cause of the dry, white, branny scales, called โscurf,โ or โdandruff,โ upon the head. This is natural, and cannot be prevented. When scurf exists, the only necessary application to remove it, is the frequent use of the hair-brush, and washing with pure water.
Observation. The secretion of the oil-glands may become impacted around the hairs as they issue from the skin, and thus prevent their outward movement in growing. The pressure of the matter deposited at their bulbs will then cause itching. The comb and the brush may be used to remove the impacted matter, and relieve the disagreeable sensation.
720. The oil is most abundant near the roots of the hair 324 A free use of the brush spreads it along the hairs, and gives them a smooth, glossy appearance. Soap should rarely be used in washing the head, as it will remove the oil which is essential to the health and appearance of the hair.
718. Upon what does the color of the hair depend? What are the causes of the hair becoming gray? What is the cause of the hair dropping out? What is related of Marie Antoinette? 719. How is โdandruffโ on the scalp produced? What is the only necessary application to remove it? Give observation. 720. Where is the oil of the hair most abundant?
721. The uses of the hair vary in different regions of the body. Upon the head, it aids in shielding the brain from injury by blows, and it likewise serves to protect this part of the system from heat and cold, thus maintaining equal temperature of the cerebral organ. About the flections of the joints, as in the axilla, (armpit,) they prevent irritation of the skin from friction; in the passages to the ears and nostrils, they present an obstacle to the ingress of insects and foreign bodies; while in the eyebrows and eyelids, they serve to protect the organ of vision.
Fig. 119.
Fig. 119. A section of the end of the finger and nail. 4, Section of the last bone of the finger. 5, Fat, forming the cushion at the end of the finger. 2, The nail. 1, 1, The cuticle continued under and around the root of the nail, at 3, 3, 3.
722. The NAILS are hard, elastic, flexible, semi-transparent scales, and present the appearance of a layer of horn. The nail is divided into the root, the body, and the free portion. The root is that part which is covered on both surfaces; the body is that portion which has one surface free; the free portion projects beyond the end of the finger.
723. The nail is formed of several laminรฆ, or plates, that are fitted the one to the other; the deepest is that which is last formed. The nails, as well as the hoofs of animals and 325 the cuticle, are products of secretion. They receive no blood-vessels or nerves. If the cuticle be removed in severe scalds they will separate with it, as the hoofs of animals are removed by the agency of hot water. The nails increase in length and thickness, by the deposition of albumen upon their under surface, and at their roots, in a manner similar to the growth of the cuticle, of which they constitute a part.
How can it be spread along the hairs? Why should soap not be used in washing the hair? 721. Of what use is the hair upon the head? About the flexions of the joints? In the nasal and ear passages? Upon the eyebrows and eyelids? 722. Describe the nails. 723. How are they formed?
Observations. 1st. The nail upon its under surface is fashioned into thin vertical plates, which are received between the folds of the sensitive skin. In this manner, the two kinds of laminรฆ reciprocally embrace each other, and the firmness of connection of the nail is maintained. If we look on the surface of the nail, we see an indication of this structure in the alternate red and white lines which are there observed. The former of these correspond with the sensitive laminรฆ; the latter with the horny plates. The ribbed appearance of the nail is due to the same circumstance. These sensitive laminรฆ are provided with an unusual number of capillary vessels for the formation of the nail, and hence they give a red tint to the portion under which they lie.
2d. Near the root of the nail there is a part that is not laminated, and it is less abundantly supplied with blood-vessels. This portion consequently looks pale compared with the laminated portion, and from its half-moon shape is technically termed lunula. Beyond the lunula, the root of the nail is imbedded in the fold of the sensitive skin, and has the same relation to that structure that any single one of the thin horny plates of its under surface has to its corresponding pair of sensitive laminรฆ.
724. The nails, from their position, are continually receiving knocks, which produce a momentary disturbance of their cell formation, followed by a white spot. The care of the nails should be strictly limited to the knife or scissors, to 326 their free border, and an ivory presser, to prevent adhesion of the free margin of the scarf-skin to the surface of the nail. This edge of the cuticle should never be pared, the surface of the nail never scraped, nor the nails cleaned with any instrument whatever, except the nail-brush, aided by water and soap. An observance of these suggestions, will prevent irregularities and disorders of the nails.
Give observation 1st. Observation 2d. 724. How should the nails be treated to prevent irregularities and disease?
Observations. 1st. When we wear a shoe that is too short for the foot, the edge of the nail is brought against the leather. This interrupts the forward growth of the nail, and it spreads out on the sides, and becomes unusually thick. It then presses upon the soft parts, and is said to โgrow into the flesh.โ The prevention is, to wear shoes of ample size.
2d. Instances are by no means unfrequent in which the power of production of the nail at the root becomes entirely destroyed, and it then grows in thickness only. When this affection occurs, it is often remarkable what a mass the nail presents. Instances are on record, where the nail is regularly shed; and, whenever the old nail falls off, a new one is found beneath it, perfectly formed. Sometimes the growth in length is not entirely checked, although growth in thickness is induced; the nail then presents a peculiar appearance.
What causes the edge of the nail โto grow into the fleshโ of the toe? How prevented?
725. In the preceding chapters, we have seen how various and complex are many of the motions necessary to maintain the life of an animal whose organization is superior to all others. We have noted the wonderful mechanism of the muscular system, in producing the varied movements of the body, the different processes by which the food is converted into chyle and mixed with the blood, and the circulation of this fluid to every organ and tissue of the system, that each may select from it the very principles which it requires for its growth.
726. Lymphatic absorption commences as soon as nutrition is completed, and conveys the useless, worn-out particles of different tissues back into the circulating fluid; while the respiratory organs and secretory glands perform the work of preparing the waste products to be eliminated from the body. Each of these processes effects a single object, and is performed in a regular manner.
727. โThey must succeed each other in proper order in propelling every particle to its proper destination, or life would be sacrificed almost at the moment of its commencement. There is, therefore, a mutual dependence of all portions of the machinery of organic life upon each other, and a necessity for some medium of communication from one organ to another, by which they may convey mutual information of 328 their several conditions, if we may be permitted to employ a figurative expression. Were there no such medium, how would the stomach notify the heart that additional exertion on its part is required, because the stomach is busy in digesting food?
725. What has been noted in the preceding chapters? 726. Show the manner in which the several processes are performed. 727. How must they succeed each other?
728. โWhen we are exerting the muscular system for a long time in some laborious employment, how else are our members to inform the stomach that they are too much occupied with their duties to spare the blood necessary in digestion; that it is requisite that the appetite should decline; and that digestion should cease for the time, even if the stomach should be oppressed with its contents? When we are thinking, how else are the blood-vessels to be told that an unusual supply of their contents is wanting in the head? or when the whole frame is weary with exertion, how, without some regular line of intelligence between all the organs, is the brain to be instructed that circumstances require that it should go to sleep? To supply the necessary medium of communication, Providence has furnished all the animals that possess distinct organs, with a peculiar apparatus called the Nervous System.โ
729. The NERVOUS SYSTEM consists of the Cerยดe-bro-spiยดnal Cenยดtre, and of numerous rounded and flattened white cords, called nerves, which are connected at one extremity with the cerebro-spinal centre, and at the other, distributed to all the textures of the body. The sympathetic nerve is an exception to this description; for, instead of one, it has many small centres, which are called ganยดgli-a, and which communicate very
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