CLES.

CHAP. III. kinds, according to the relative position of their three essential parts, the SECT. III. weight, the power, and the fulcrum. Those of the first kind have the fulOF MUS- crum in the centre, in those of the second kind the weight is in the centre; while in the third, the power is in the centre; the bones are of this last description, in which the power is placed between the fulcrum and the weight. The motion of the forearm may be taken as an example of the effect of muscular contraction, and the manner in which it is produced. When we wish to raise a weight by bending the elbow joint, it is effected by a muscle below the shoulder, which has tendons inserted into the top of the bone of the forearm near the elbow.(u) Let Nos. 1 and 2 represent the forearm; No. 3, the weight to be raised; No. 4, the Biceps muscle, arising from the shoulder, with its tendon inserted into the forearm below the elbow; No. 5, the upper arm, small in the middle and large at the extremities; and No. 6, the elbow joint, being the fulcrum, thus:

6thly. The action of muscles.

By the contraction of the Biceps muscle, 4, to a small extent, the bending the joint, 6, is occasioned, and the weight is carried up to a height proportionate to the length of the forearm, or in other words, the hand forms a part of the circumference of a circle of which the elbow is the centre. This consideration of the manner in which the muscle acts, shows that the mechanism of the animal body is calculated to produce a great loss of absolute power, but such power is thus sacrificed to afford increased velocity and symmetry of form, which, if the muscle were otherwise placed, would be clumsy and awkward.(x)

6th. Their Action explained.-The cause of the contraction of muscles seems to be imperfectly known.(y) Dr. Bostock, on Physiology, concludes his valuable observations on the subject, by stating, that in the present state of our knowledge, contractility ought to be regarded as the unknown cause of known effect, a quality attached to a particular species of matter possessed of properties peculiar to itself, and which we are not able to refer to any general principle.(z) But MM. Prevost and Dumas have, as we have seen, recently attributed muscular contraction to electricity, and by the nerves coming in contact with the muscles.(a) And Dr. Edwards, remarking upon this hypothesis, himself concludes, "d'ou il paraitrait resulter que les contractions sont dues à l'electricité produite par le contact du nerf et du muscle."(b)

The action of muscles never intermits, and is only diminished in the sleeping state; though where the sleep is profound and lethargic, the

(u) Winslow, sect. 3, art. 5; and Mem. Acad. pour, 1720; 1 Bost. 147.

(x) 1 Bost. 147 to 157; 1 Dunglison, Phy. 324 to 340.

(y) 1 Bost, 157 to 174.

(z) 1 Bost. 174; 4 Good, 223.

(a) See Ante, 87, and extracts, 3 Bost. 281 to 288, and Quain, Anat. Plates, p. 3. (b) See extract, 3 Bost. 284.

diminution amounts to almost a cessation, except in the involuntary organs. When muscles are not exercised, the vis insita is very slightly exerted, but we can still trace its influence by the position which the limbs assume, and discover the strength of the antagonizing muscles, (c) and in disease, especially in children, the observance of the muscles during sleep will assist in discovering the state of tone.(d)

CHAP. III.

SECT. III.
OF MUS-

CLES.

lar and ner

In considering the nervous system, we shall examine the connexion 7thly. The between the muscular and nervous system. (e) To every muscle there connexion are two distinct sets of nerves, the one to excite and give the muscles between their power of motion, the other perceptive nerves, appropriated to the the muscusensitive faculty of such muscles, and to communicate the sensation to the mind. (f) Prevost, Dumas, and Dr. Edwards appear to attribute tems. muscular motion to the effect of electricity, occasioned by the contact of the nerves and muscle. (g)

vous sys

SIS.

In order to promote the symmetry of form and the facility of motion, II. OFTENwe find that in many cases the flesh of the muscle itself is not inserted DoNs and directly into the bone which is to be moved, one or both of the ends ter- APONEUROminating in membrane, which, according to the situation or use of the part, is either converted into a strong cord constituting a Tendon, or is spread out into a membranous expansion technically called an Aponeurosis (from ano and veupov.) (h)

The tendons are the continuation of the interstitial cellular membrane of the muscle, and may be unravelled into a web.(i) But tendons, as distinguishable from muscles, have been supposed by some to be dead and unorganized, and have no visible nerves, and are insensible and not contractile,(k) and they possess very few if any blood vessels; and no vessels have been discovered in them for the purpose of secretion or absorption: but the better opinion is, that tendons have an absorbent apparatus. () Indeed if they have not, or if, as supposed, they be unorganized, how could a ruptured tendon reunite and again become useful, as certainly in some cases occur, in case of the rupture of the Tendo Achilles.(m) In their chemical composition tendons nearly resemble the most compact membranes; their basis appears to be a coagulated albumen, united to different proportions of jelly and mucus. They contain no earth, and only a small quantity of saline matter. (n) The principal use of tendons is to connect the muscles with the bones, and serve as cords or ropes to transmit the action of the muscles to a distant point, and in doing this their operation appears to be entirely mechanical. (0) Unless the muscle is directly connected with a bone, tendons are seldom found, and, therefore, there are no tendons attached to the muscles of organic life.(p)

Muscles and tendons are subject to several diseases, particularly rheu- III. Of the

CHAP. III. matism, spasms or tumours, each of which will hereafter be fully consiSECT. III. dered, with their remedies.(q)

OF MUS-
CLES.

the mus

cles and tendons.

In cases of sudden death from lightning or electricity, or a blow upon the stomach, or the bite of some venomous animals, or from some acrid diseases of vegetable poison, as laurel-water, or from exercise, or violent mental emotion, occasioning sudden extinction of life, the muscles will be found in a state of relaxation, and to have lost their susceptibility to contractility by any stimuli, and the blood will be non-coagulable; circumstances important to be attended to when there is any supposition of criminal death,(r) whilst it is the opinion of some pathologists that the force of muscular contraction through the system generally is increased in inflammatory fever. (8)

IV. Of the

muscles

and tendons.

Muscles and tendons are also liable to various Injuries, as ruptures and Injuries to wounds,(t) which it will be more proper to consider in a subsequent chapter. Ruptures even of the Tendon Achilles are capable of reunion by relaxation and care. (u) When a muscle has been divided across by a deep wound or cut, the union which may result is always incomplete as regards the muscular fibres. The muscle may be said to unite as a whole, but the muscular fibres not. The union takes place between the cellular tissue investing the opposite surfaces, and the union presents a firm line of fibro-cellular material, at which the muscular fibres of each half terminate. But the injurious consequences of deep transverse cuts across muscles may be long if not permanently felt in reducing or retarding the power of the limb, and in that view it may frequently be important in judicial inquiry to be able to enumerate and establish in each case all the probable consequences of such an injury, so as justly to increase the measure of compensation for the injury.(v)

V. The number,

names, and description of each

The enumeration of the particular muscles, from the cranium to the lower extremity of the human frame, would follow the same order as that observed in the arrangement of the bones, and the joints and ligaments.(w) The muscular fibres of the neck, back and loins, those on which all the muscle and complicated movements of the vertebral column depend, compose more than 300 distinct muscles in the whole; (a) and it is said that the entire human body possesses about 450 muscles or upwards, but varying in number in different individuals: it is thus furnished with a double advantage, namely, an extreme agility of motion in particular parts, and throughout the whole a surprising degree of strength and endurance of labour.(y)

tendon.

The muscles have been generally arranged and examined in the order of their several layers, of which there are four on the back, and elsewhere usually two; and of these are considered, first, those most external, and then

NERVES.

successively the ulnar layers, until the bones are exposed.(z) It has been CHAP. III. justly observed, that their present nomenclature is very perplexing, and SECT. IV. not uniform upon the same principle; for sometimes the name is taken NEUROLOfrom their situation, at others, from their action and use, and sometimes GY, OR THE from their order of dissection (a) Very useful Tables of all the muscles, showing their names, action and use, have been recently published,(b) and the student must study the observations of Dr. Quain, in connexion with his explanatory plates. (c)

SECTION IV-OF NEUROLOGY, (d) OR THE NERVES.

The bones with their joints, and the muscles and tendons, though The utility capable of motion, would be inactive, unless excited and stimulated by the of the Nerves. These communicate sensation from the different parts of the nerves in body to the sensorium, and other nerves excite the motion of the muscular stimulating fibres; (e) but as they form parts of what is termed the nervous system, encing the they will be more properly and particularly considered hereafter.

and influ

muscles to

It may suffice here to observe, that with respect to the relations which motion. the different parts bear to each other, the Brain is the centre of the nervous system, or that part to which all the others are subservient, and that some Nerves receive impressions from external objects, and transmit such impressions to the brain, where they become sensible to the mind, constituting perceptions, which is one mode in which the nervous system operates.) The second mode in which the nervous system operates is by its reaction on some of the organs of the body, an operation which, with respect to the succession of events, is the reverse of that just noticed. Of the actions of this description one of the most importance to our existence, and the most frequently exercised, is the faculty of voluntary motion of the muscles. Here the affection originates in the brain, in which some change takes place; this is transmitted down the nerve into the muscle, where an effect is produced on the fibre, which causes it to contract, and in this, as in the former case, all the three stages are equally essential. (g). It will here suffice to notice that the nerves, as they appear to the eye in every part of the frame when dissected, are white cords, flat, round or irregular, bound up in firm membranes, and blood vessels accompanying them; and each nerve consists of many fibres, and the cellular texture and blood vessels are interwoven with such fibrils. (h)

(z) See 1 Horn. Anat. 391 to 500. (a) Quain's El. 2d edit, and Quain's Anatomical Plates, p. 1.

(b) Quain's El. 2d edit. 383, 385, and Burgess and Hill's Tables.

(c) A. D. 1833, in course of publication by Taylor, bookseller, Gower-street.

(d) Neurology, from vugev, a nerve, and yes, includes properly the description of

the nerves, brain, and organs of sense.
As to the nerves in general, 1 Bost. 179,
and post; 1 Dungl. Phy. 41 to 64.

(e) Jackson, Princ. Med. 127, &c.; 4
Good, 4.

(f) 1 Bost. 175, and post.
(g) 1 Bost. 232.

(h) 1 Bell, Anat. 365; 2 Horn. Anat.
327, &c.

CHAPTER IV.

OF THE FUNCTION OF RESPIRATION, AND INCIDENTALLY OF VOICE, SPEECH,
AND OTHER SOUNDS, AND THE SEVERAL EFFECTS OF RESPIRATION. (a)

quism, Whistling, &c. Change
of Voice at Puberty.

7. Trachea or Windpipe.

8. The Thyroid Gland.

9. The Thorax.

10. Diaphragm.

11. The Bronchial Tubes.

CHAP. IV.

12. The Lungs

SECT. I. RESPIRATION.

2. Internal construction.
3. Dimensions and Capacity.

4. Several Contents of.

1. The Bronchial Arteries.

2. The Pulmonary Arteries. 5. Colour of.

6. Size and Weight of.

7. Muscles and Motion of.

8. Nerves thereof.

13. The Pleuræ.

Section II. The immediate and principal
Functions of these Organs, namely,
Respiration.

Section III. The more remote Functions
and Utility.

Section IV. Of Defects, Diseases, Disorders, and Injuries to these Organs.

1. The Mediastinum dividing Section V. Of Transpiration, Evaporation,

them.

and Transudation.

General PERHAPS, of all the organs and functions, those of Respiration should view of the most excite our admiration, as well in respect of their structure as their function of durability, notwithstanding their very delicate structure and incessant respiration. employment. The Lungs are composed of exceedingly delicate and

small air cells, and the pulmonary blood vessels from the right ventricle of the heart, containing the dark blood, pass by and around these air cells; and the atmospheric air, containing oxygen and renovating principles, is inhaled in rapid succession into such air cells, and absorbed through the delicate membrane of such cells into the blood, in those vessels, whilst, through the same media, the carbon and other noxious particles of the blood acquired in the course of circulation, escape and are carried off from the system; and although it must be admitted that a great proportion of mankind, especially in England, die from disease of the lungs, yet it is astonishing that so delicate a membrane should be capable of enduring and performing its office during even protracted life. We are here to consider, in detail, all the organs and functions of Respiration, and incidentally, the organs and functions of voice and speech, and various other sounds.(b)

Respiration (a compound of the Latin re again, and spiro or spiritus,)(c) commonly called breathing, consists of the drawing into, inhaling, or technically called inspiring, atmospheric air into the lungs, and then forcing out, expelling, or technically expiring, from the lungs the air therein, whilst at the same time the blood is transmitted through a set of vessels, so situated in the lungs as to enable the air to act upon it, and to

(a) In general the circulation of the blood has been treated as the principal vital function, and therefore first considered; and respiration, or, as some term it, the atmospherization of such blood, has been treated as a subordinate function; 2 Bost. 1; but in respect of its indispensable utilities, as well directly as re

motely, we have in this work given respiration precedence.

(b) See in general, as to respiration, voice, and speech, El. Blum. 110 to 153; 1 Good, 338 to 361; 1 Bost. 1 to 246; Jackson, Princ. Med. 403 to 455; 2 Dungl. Phy. 66 to 115.

(c) 2 Par. and Fonb, 11.