Complete Text (Part 3)

of the two bones and connected with them by strong ligaments also takes part. The back portion of the knee- joint is called the ham. The two bones of the lower thigh thicken at their lower end into the inner and outer ankle (joint) and form with the talus the joint of the foot (astralagus). The latter is one of the seven bones of the tarsus, of which the heel bone (oscalcis) is the most important. The tarsus, the middle foot and the toes form the foot, which is again divided into the back of the foot (the instep) and the sole. In a standing position the foot rests on the heel — formed by the heeljoint — and on the balls of the big and little toes, so that the outer edge of the foot touches the ground. The heeljoint and the balls possess as fulerum of the foot a very thick skin; that part of the sole lying between them is somewhat arched upwards and is called the arch of the foot. In some persons the latter has sunk so much that in standing the foot touches the ground with the whole sole and with the inner edge of the foot. A foot misshaped in that manner is called a flat foot. The strong sinew, which stretches like a stringlike extension of the muscles of the calf of the leg to the posterior end of the heelbone is known by the name of The tendon of Achilles. § 12. The viscera of the thorax. (Fig. 4.) The tissues enclosed in the large cavities of the trunk are called viscera. In the cavity of the chest lie — as viscera of the chest — the two lungs and the heart. § 18. The Lungs and Breathing. The lungs, of which the right is composed of three, the left of two super-imposed lobes contain like a sponge numberless very small cavities, which are called vesicles of the lungs. From the vesicles proceed thin elastic tubes, which join in wider tubes and finally open into the large branches of the windpipe, one branch of which leads to each of the five lobes of the lungs. Two wide tubes, one of which receives the Some parts of the Body and their Functions. 13 three branches of the right lung, the other the two branches of the left lung join together as the windpipe. (Fig. 5.) The latter runs into the middle line of the neck and in ig. 4. Thoracic und abdominal viscera in man. a, Lungs. hb. Windpipe. c. Larynx. d. (esophagus. ¢. Diaphragm. f. Stomach. g. Duo= 4 Di denum. 4. Liver. é, Gallbladder. k. Small intesti 1. Largo intestine, m. Coecum, u. Urinary bladder. ‘The dotted line schows the contour (outline) of the heart, which for the sake of clearness must be considered to have been taken out, (remored.) its upper end passes into the Larynx, which opens into the fauces and thus is connected with the outer air through the openings of the mouth and the nose. The outer surface of 14 ‘A. The structure of the human body. the lungs is covered by a thin membrane, the pleura pulmo- naris; the interior of the chest is lined with the pleura (costalis). By the uninterrupted activity of the lungs, called breath- ing, the air, which man requires to live, is introduced into the body. We distinguish between inspiration and expiration; in inspiration the air from without passes through the wind- pipe and its branches into the expanding lung- vesicles, at which action the lungs are inflated like a bellows; while in expiration the used-up air (cf. § 16 and 21)is driven out from the lung-vesicles, which pro- cess makes the expanded lungs 4 sink down again. To inspi- ration and expiration corre- spond the regular breathing a, 1) ae = = motions of the chest, which — are perceptible as expansion =f and contraction as well as = rising and falling. The air = expired is warmer than the = air which we inhale; it con- = tains less oxygen than the SZ latter, but is richer in car- & bonic acid and moisture; that the former contains more water > can be shown, that cold ob- jects, for instance mirrors be- come dulled when breathed Fig. 5. upon, and also, that the breath, Iarynx A and Windpipe B with its branches. issuing from the mouth chan- ges in cold weather into visible vapour. The number of respirations of an adult person is from 16 to 18 in a minute, but this is increased in rapid walking or running, in ascending stairs or mountains and also in several illnesses. Children when at rest and in good health also breathe more frequently. $14. The Larynx; the voice and speech, During the expiration tones can be produced at will in the larynx, which constitute the voice. The larynx, whose cartilaginous walls can be felt in the centre of the throat, contains in its interior the Some parts of the Body and their Functions. 15 two vocal cords, extending close to each other from front to back. When at rest these are relaxed and lie so far apart, “that a large opening between them allows free passage to the air which we breathe; but by means of small muscles in the larynx they can be extended and brought nearer to one another. The exhaled air makes them then vibrate and thus produces according to the tension of the cords higher or lower tones, which we observe in speaking and screaming, but most clearly in singing. With the aid of the tongue, the palate, the teeth an the lips we can perfect our voice to speech. § 15. The Blood; the bloodvessels; the heart and the circulation of the Blood. A part of the inhaled air mixes itself inside the lungs with the blood, which courses through the body during life in unceasing circulation. The blood is red and viscous; it consists of the colourless blood fluid (plasma) and innumerable little blood corpuscles. (Fig. 6.) By far the greater part of these are shaped like a coin and a yellow reddish colour (red blood corpuscles); a smaller number are round and colourless (white blood corpuscles). Outside the body the blood generally coagulates, as a gelatinous mass and the bloodwater (serum) separate from each other. The blood is to be found partly in the heart, partly in conduit-like bloodvessels. The larger ones have elastic sides (Adern); they are divided into arteries, in which the blood flows from the heart into the other parts of the body, and veins, which bring back the blood from the body to the heart. The Heart (Fig. 7), surrounded by a skin-like substance, the pericardium — as in a sack — lies in the front part of the left half of the thorax. It has about the size of the fist of the man, to whom it belongs, and in shape it resembles a cone whose base lies behind the middle part of the breast bone, and whose apex touches the front wall of the chest in the interval between the 5 and 6" left ribs at a distance of a hands-breadth from the lower third of the breastbone. While the anterior wall of the heart lies close to the wall of the chest for the most part, the posterior wall and a portion of the upper and outer edges is covered by the left lung. The heart consists of muscular masses and encloses a cavity which ‘is divided into four sections by one partition wall running vertically and another running diagonally. The two upper sections lying close to the base are called the right and left auricle; the 16 A. Tho structure of the human body. two lower, which lie nearer to the apex are called the right and left ventricle. Each auricle is connected with its corre- sponding ventricle by an opening of the diagonal partition wall. ° From the left ventricle of the heart comes out the great artery of the body, or aorta. This at first runs somewhat up- wards, then makes a bend backwards to the spinal column, then from there downward to the pelvic cavity, where it divides into two ,,Adern“ (arteries) for the two lower limbs. At the Fig. 6. Blood corpuscles, greatly enturged. u. Red; b, white, blood-corpuscles; ¢. red blood-corpuscles, lying besides cach other, like @ roll of gold; d. dito, seen singly laterally. bend proceed upward from the great aorta the arteries for the head, neck and the upper limbs, while the arteries for the viscera of the thorax and abdomen come out from the aorta in its downward passage. All arteries divide into branches, till finally very thin, small arteries — capillary vessels — only visible by the microscope result, which are spread like a dense network all over the body. Through the uniting of capillary vessels are formed the small veins, and from these the larger veins are formed. The latter finally unite in the two great venae cavae, of which the upper brings Some parts of the Body and their Functions. 17 back the blood from the head, neck and upper limbs and the lower the blood from the other parts of the body and pour it into the right auricle of the heart. The portion of the circulation, which we described thus far, that between the left ventricle and the right auricle of the heart is called the great circulation, or the ,Koerper- Kreislauf“ (circulation in the body. Fig. 8 and 9). From the right auricle the blood passes into the right ventricle; then it enters inside the pulmonary artery proceding from there into the small or lung circulation. The pulmonary Fig. 7. Section of the heart (Diagramm). a. Left auricle. 6, Right auricle, ¢. Left ventricle. d. Right ventricle. artery divides in the lungs just like the other arteries of the body into gradually smaller branches; the capillary vessels of the lungs unite and form the pulmonary veins, by which the blood is brought back to the left auricle and thus into the great circulation. $16. Relations of the circulation of the blood to re- spiration. The circulation of the blood is cffected by the contractions of the heart; these take place in an adult person about 72 times in a minute, in old age less frequently, more frequently in children, and they affect in regular alternation the auricles and the ventricles. As soon as the ventricles contract, the bood flows from them, as from a squeezed india- rubber ball into the arteries; at the same time the auricles expand and as it were suck in the blood from the blood- vessels. As soon as the auricles then contract, the blood 2 18 A. The structure of the human body. taken up by them flows into the ventricles and expands them. As soon as the auricles expand the apertures between them and the ventricles are closed by valve-like arrange- ments, so that the blood which has already passed into the ventricles cannot flow back again. Other valves prevent a re- flux of the blood from the great body artery and from the pulmonary artery into the ventricles of the heart. By some diseases the valves are so changed in their shape - than they are no longer capable of closing. Such defects in the valves of the heart may lead to disturbances in the circulation, since the blood on the expansion of the ventricles and the auricles partly flows back into them, expands them immoderately and blocks the veins. Each contraction of the heart occasions a gentle motion of the chest, especially at the apex of the heart; this is the heart-beat, which is externally visible and can be felt in many men. From the influx of the blood, expanding the arteries re- sults the beating of the pulse, which may be felt by gentle pressure of the fingertips in the superficial arte- ries, for instance in the radial artery inside the radius and close above the wrist. The strength and fre- quency of the beating of the pulse is altered in consequence of mental excitements and in many sicknesses, especially in cases of fever an increase in the number of pulse beats is usually observed. During the circulation a change takes place in the colour of the blood, which is connected with the respiration. A part of the oxygen, contained in the inhaled air (cf. § 34) is taken up into the blood by the capillary vessels of the lung vesicles, which are provided with walls letting through the air, com- bines with the colouring matter of the blood contained in the ~~ Fig. 9. Circulation. Windpipe Left carotid artery Aortic arch Upper vena cava Left auricle Pulmonery artery — _ Pulmonary vein Right auricle Loft ventricle Right ventricle f Brachial artery Lower vena cay: Lung Portal vein Descending sorta Spleen Femoral vein — a Femoral artery Fig. 8. Vaseular structures. ‘The red vessels are arteries; the blue veins; but the pulmonary artery is coloured blue, and the pulmonary vein red, on account of the character of the blood, carried by ‘these vessels. Some parts of the Body and their Functions. 19 red corpuscles, and thus produces the bright sclarlet red appearance of the blood. This colour remains preserved, while the blood flows through the left auricle, the left ven- tricle and the arteries of the body; in the capillary vessels of the great circulation the oxygen however is given up by the blood to the surrounding tissues, and an approximately equal quantity of carbonic acid is received instead, from which the blood acquires a blackish red appearance. Thus coloured the blood flows through the veins, the right auricle, ventricle and the pulmonary arteries to exchange in the lungs the carbonic acid, which it has received for fresh oxygen. The carbonic acid which is removed from the organism through exhalation is produced in the tissues of the body by a pro- cess, similar to combustion (cf. § 21), 3 § 17. Lymph, Lymph- vessels and Lymph-glands. In addition to the arteries and veins, which convey the blood, there are still other vessels in the human body, which con- tain an almost colourless fluid, called lymph, which vessels are named lymph-vessels or absorbent vessels. Their very thin terminal branches, extending everywhere absorb their tissues from the bodily tissues and convey it into the upper vena cava through a great lymph vessel stretching upwards in front of the spinal column through the thorax. This vessel has a diameter of $cm. Along all lymph-vessels are inserted the lymph-glands. These are varying in size from the head of a pin to a bean and contain in their interior innumerable small cells, resembling the white blood corpuscles. The lymph flowing between these cells leaves behind it as in a filter any impurities which it may have carried with it. Such im- purities lead to a swelling of the lymph-glands, if they (the impurities) contained certain noxious matters absorbed from diseased bodily tissues or from wounds. § 18. Viscera of the Abdomen. (Fig. 4.) To the viscera of the abdomen belong particularly the organs of digestion, the organs for the secretion and flowing off of the urine and the spleen. The organs of digestion are the stomach, the intestinal canal, the liver and the pancreas. § 19. The stomach, the oesophagus, the intestinal canal, the mesenteric and the omentum. The stomach is a longish sack, with sides like skin; it lies crosswise immediately unter the diaphragm in midst of the abdominal cavity, the front - wall o* 20 A. The structure of the human body. of which it touches near the cardiac region, or pit of the stomach. The more spacious part of the stomach on the left side is nar- rowing above and at the back to the esophagus; this forms the connection between the cavity of the mouth and the stomach; it is a sack of about the thickness of a finger with an elastic side in front of the spinal column, at the neck behind the windpipe, in the thorax between the great bloodvessels down- wards to the diaphragm and penetrating this latter opens into the stomach. In its part to the right the stomach narrows like a funnel, until it continues behind into the bowels. The place of transition which sometimes is compressed (constric- ted or gripped together) so firmly by a muscle surrounding it like a ring, that the cavity of the stomach is shut off from the interior of the bowels as if by a valve, — is called the pylorus. The intestinal canal is formed like a sack with mem- branous walls, whose length is about six times that of the human body. We distinguish in the bowels the narrower small intestines from the wider large intestine (commonly called great gut). The narrow intestines, whose uppermost part, bounding on the stomach and about twelve fingers in length is called the duodenum fills with its folds the greater part of the cavity of the abdomen. In the lower part of the abdomen, to the right just above the hip- bone it opens into the large intestines, the first part of which lying im- mediately below the soft covering of the abdomen forms a sack shaped projection downwards, called the caecum. Hanging down from this is a vermiform continuation, an intestine, about as long as a finger and somewhat thicker than an earthworm. The caecum and the vermiform prolongation sometimes develop an inflammation which seriously threatens life; in some cases indigestible bodies e. g. cherry-stones, which accidentally got into the vermiform continuation are the cause of such an illness. From the caecum the large intestine procecds first upwards, then it turns in front of the anterior wall of the stomach to the left side of the cavity of the abdomen, - then descends into the pelvis and enters this, resting on the os