Section IV. OP THE HUMAN BODY. (Part 1)

Section IV. OP THE HUMAN BODY. Man, although the most perfect product of the cre- ation, lias a body wbicb closely resembles, in its inter- nal structure and vital phenomena, tliat of the inferior B«clt<l, loc. cit, p. IS. c iU u rxtkhnal porm. P animals. The preceding observations lead, ihen, in n natural order, to the examinntion of the human orga- nixation, which is the immediate object of the present work. The investigation of the human frame presents two ''points for coniiiderAtion : I. The extemnl configuration ""or form. 2. The intwtiid composition or texture. The human body, like that of all orgunized beings, •'htis a rounded form, which is not only evident in its ex- ternal contour, but also in its different organs, and even in the minute particles of which these are composed. Thb rotundity depends principally on the laige pro- portion of fluids which enters into the composition of animals. This ta seen in the young child, in whom the limbs, the fiicc, &c., are distinguished by their rounded forra ; whilst, in old age, when the humours are con- siderably reduced in quantity, the bod)' loses much of its original form, and becomes unequal and irregular upon the external surfoce. '■ TTie length of the human figure greatly exceeds its breadth and thickness. The degree of this excess is subject to -ariation in the different epochs of life, and also according to the robnstneA!) and embonpoint of the individual. This disposition i<i most developed in the extremities, where the bones, mu-scles, ves.ieU, and nen-cs arc distinguished by their length. It is, however, frequently met with in the trunk. Some anatomists have endeavoured to prove tliat there is a radiated orrange- ment of the organs, but, iJthough the vascular and the ncr'ou.H R)'slems do, in some degnie, observe this order, yet it wo»dd be incorrect to receive it as one of the chamcteristicB of the human fomi, ■•'• In all the superior nnimuls, and consequently in man. STMMETRV. there is a marked srmmetr)- in the exterior and partly b the interior of the body, so that we may regard the body as being divided into two lateral and correspond- ing halves. The symmetry is not equally defined in all ports of the body ; it is most distinct in the organs which he- long to the animal tVinctions, and least so in those which are connected with nutrition. Thus the hones, the muscles, the nerves, and the organs of Uie senses aic double; whilst the stomach, the intestines, the liver, the spleen, &c. arc single. There are, howe'er, many exceptions to this law ; for example, tlie kclir)-mal glands, the salivary glands, the mommit!, the tusticlcs, the kidneys, and the blood-vessels are nearly symnie> trical. There are several parti which are more sym- metrica] at the period of their formation than after- wards ; thu« the liver is at that time more equally di-ldcd by its broad ligament j the heart is placed more perpen- dicularly in the chest, and Its two sides nearly corre- spond in their size and in tlie thickness of their pa- rictes. This dixHston of the body is effected by a vertical plane, which we may imagine to be placed exactly Id the median line. This plane forms on some parts of the external surface, a peculiar appearance, which is termed raph£; as the raph^ of the perinxum, of the scrotum, &e. In many of the internal parts there is a partition in- stead of ft mere line of demar<^aliou. This is seen in the spines of the frontal and occipital bones, in the tidx major, in the septum lucidum, in the septum narium ; there are also traces of it in the mediastinum, the sus- pensOTy ligament of the liver, &c. These different lines ^ SYMMETRY. anr! partitions indicate the places at which the two siifrt of the body and of the various organs, which urc s<'pa- ratcd in the embryo, are subsequently united. There are several organs placed on the median line, which have not at first sight a sj-mmetriaJ uppcitranct, but which possess it in principle ; wc have examples in the tongue, in the tnrynx, in the thyroid gland, in the prostate gland, in the heart, and LTen in the vertebral column. ' ' The analogy between the upper and lower parts lif the body is not so strongly chanicterized, as that which we have traced between the lateral ports. Still it is ceri tain, that the divisions of the upper extremity have con- siderable resemblance to those of the lower: thus the arm corresponds to the thigh, the fore-arm to the leg, and the hand to the foot. Tlie differences which are obsen'ed between these parts, depend on the diversity of function of the upper and lower limbs. Some anatomists have also compared, but with little reason, the lumbar portioD of the spine will) the cer'ical ; the large ver- tebra; of the Sacrum with the bones of the head ; and the OS coccygis with the lower jaw. The comiMirison has even been carried so far, that it is said, by Mcckdf the apparatus of respiration is companible to the urinary^ and tlie thyroid gland, tlic thymus gland, the tongue; and the nose, to the orgims of gunemlion. Tliis ap- pears to he forcing a resemblance which does oob' exist in nature. The same anatomist also contends for an aiudopy hotwecn the anterior and posterior surfaces of llie body, and \vith this idea he ha.s compared the sternum and linca alba to the vertebral column. This comparison is as objectionable as the last, ^'J The detMls which 1 lutve mentioned, sufficiently prore DIVISION OF BODY. 21 .Ihut lliv body lias a symmotrica] form. But in demon- strating this fuel, it is not pretvadvd that the symmetry is mathematically correct. There are many exceptions to it, and in some respecte it is porticulurly imperfect. The human body is divided into throi^ parts, viz., the head, the trunk, and the extrenuUes. The first distin- guished by its rounded 6gtire, is plnced on the upper pari of the trunk, on which it is supported. It lodges the central organ of the nervous system, the ot^ns of the senses, with tlie exception of that of touch, and the organs of mastication. The second paxt, or the trunk, is flattened anteriorly and posteriorly. It consists of the vertebral column, of the thorax, and of the abdomen ; the first contains the nervous mass, which is called the spinal cord ; the second receives the central organs of the cir- ctJation and of respiration, and tlic third encloses the af}[uiretu$ of digestion, of the secretion of urine, and of generation. The extremities, which are four in number, are distinguished into the superior or thoracic — and in- ferior or abdominal. They are characterized by their lenglJi, wliich greatly exceeds their other dimensions. These mraabers are di%ided into several parts, which are joined together in tlie numerous articulations, in such a manner, as tu be admirably calculated for varied and extensive motion. Tlie different parts of the head, trunk, and extremi- ties are subdivided into a certain number of regions, the situation and the extent of which, arc principally determined ,by the bones. A perfect knowledge of the relations of these regions is indispensable to the Bur- geon, a.s it forms the most certain guide to the situation of the %'arious and important organs which are concerned vritb Ae perAnmance of the different opcrtttions. Th« study of tills branch of our xcienct* livluiigs to what has bc>«Q judiclou^y called, topognipltictd anatomy. The human body consists of an usstmblagc of fluid and liolid ports, which hnvir a mutual influence on Cftcb other, and which (experience ut every moment of their exHtence, certain important and necessary changes. They are so intimately combined with each other in the organ;) of tlie body, that it is impossible to effect an entire separation between them. The natttre of this comhiDation, which no art can imitate, is but imper- fi-ctly understood ; it doubtless depends upon the in- fluence of life, so that when this is destroyed, the union which had previously existed begins to yield to eliemical agents, and the decomposition of the organic textures is the speedy result. In studying the wonderful structure of our frame, we should obsene the same method as in investigating the nature of any other material body : that is to My. we should endeavour to sepnrate the fluid IVom the Mjlld parts ; wo should examine thesse individually, in order to aacertuin their properties, tiieir tiifferenci-s, and their uses ; in fact we should annlysc, aa far as thi» is possi- ble, the aniinid body, so as to determine the nature of its conbtitULnt parts. This mode of procedure is well calcidatcd to unravel the intricacy of tlic human organ- ization I but in order to complete our knowledge of the dl.spo.sition and operations of this compliciite^l machine, it is nt-cessiUT to reverse the method of examination ; to trace, in a synthetic order, the various combinntiona of the fluid antl solid materials ; to study the prop«-tl« and Msvn of the different or:gan» ; and, lastly, to com- OF THl! b6T>Y. 't5 pare the relations that exist between them, so that the share which each enjoys in the prociuction of the vitel (riienomcna, may be properly distinguisherl. ^ ■ The researches of animal chemistry, to which anatomy ■qd physiology are so deeply indebted, b&ve shewn that 4he human body is composed of a great number of elementary substances, which are termed its ultimate principles. The exact numl>er of these simple matcriab has not yet been determined, but tlie following are gene- rftlly admitted : — ,^ ELEMENTARY SUBSTANCES. I. Aioie. 9. I>Dtuaiun. V S. CuboD. 10. Msfpoium. 11. Iron. 4. Hydi^icD. • 12. Chlorin. S. Phoapbcnn. 13. Mai>trHn»of 6. Cttlcium. 14. Siliciom ' II 7. Sulphur. 15. Fluorio? f. 6. Sodium. 16. lodia > ^'^* The combination of these elements in different forms and proportions, produces certain compounds which are called the immediate or proximate principles of forma- tion. They vary considerably according to the age of the individual, the state of health, and other circum- stances ; so that it i£ very ditHcult to ascertain what number really belongs to the composition of the healthy ',' PROXIMATE PRINaPLES. J I. OclUiD. * fi. Mucin. ^ ^, 2. Albumen. 7. Um- 3. Fibrin. 8. Pioomel. * ' 4. Coloutinff Mmi«t of the Blood. 9. Sugar of Hilk. (Olcin. ,^f S. FtU^Hattct.. ^Stearin. (CholottriQ. ACIDS. lai 1. Phetphunc. S. Uric. 7. Oxtlie. S. Aixiw. 3. Cutionic 4. Solphonc. 5. Mntatic. 0. Bui]me; 10. Purpuric' It. Milir» 6. Beinoic. » The omuigctncut of these constituent priQcip](%, tnd the form tbey present in the fluid atid solid piu-tii of the body, have, for a couaidcraWe period, occupied the at- tention of tlie most ctlebrnlcd anatomists of Europe. Of the various means that have been adoptijd lu eluci- date this subject, none have been so extensively em- ployed as the microscope. The raagmfyiiig powers of this instrument, by enabling us distinctly to perceive the mortt minute particles of matter, have thrown great light ' on the intimate composition of organized bodies. But in acknowledging the advantage which has beeu deri\ied from microscopical researches, it is important to state, that much of their value is destroyed by the frequent contradictions they exhibit in their resulLs. These dis- crepancies ha^-e proceeded from se^'cnd causes, of which the most influential are the imperfection of the instru- ment that have been employed, and the optical decep- tions that haw so freijuently misled even tlie most skil- ful exiierimentalists. In the present djty this uncertainty exists to such a dcgra-, that few points concerning the intimate textures of tJic body can be considered as lirmly established ; and, therefore, the readei must recei"c with caution idl dt-duction-s that are derived irum this source. We arc indebted to J. F. Meckel, the celebrated pro- ftssor of anatomy in the University of llallc, for some important obscr^-ations upon the minute texture of the OP TffB BODir. idi l» aoimfil organization. In hift excellent ^fa^ual of Ana- tomy,* in speuking of texture, he says:—" It is pos- sible to reduce tbe compound parts into substances that arc more simple, and which in their turn differ from each other according to their degree of simplicity. The ultimate constituent parts may be reiluced by ana- lysis into two substances ; one nf these possesses a de- termined form, which is not the case with the other, Although this is also capable of configuration. These sub- stances consist, one of globules, and the other of a matter which is susceptible of coagulation. The latter sub- stance, citherby itself or united with the globules, forms, when it is liquid, the fluids, and when it is coagulated, the solids of the body. These two material elements are not ()olh contained in ewrj' fluid or solid ; the glo- bules, however, are never met with by themselves ; they are always plunged in the mid^it of the coagulated or coagubble substance. '* The name of gIob\iles is not strictly applicable to the above mentioned particles, for it is proved that many of them, especially those of the blood, have not the same thickness in every direction, but tliat they art flat and lenticular. Howc%'cr they are every where rounded, never beiog found angular ; hut their form, their volume, their number, their colour, and their chemical composition neither rcscmhle each other in different snbjecfc* nor in different part* of the same subject ; they also vary ac- cording to the period of life ; so that the above charac- t^ are transient, and liable to irregularity. Thus, with respect to form, the globules appear lobe more com- pound in some purts than in others. In the blood they * MnMol d'Aoiiluniif!, Otnfnle, Dactiplive, el PuUiotoBiquc. 1>aa»- lattA into Pnmch &gt;y M. M. JoutJan and BraKbcl. J INTIHATB STRUCTCRB tre composed, according to many observers, of a cen- tral solid part, and of a hollow and vesicular part, kvhich encloses Uic former without adhering to it. Every Ivhere eUc their structure appears to be more simple, I for we only perceive in thnm utie of tliese two partA ; [but whaterer may be the region of the body in which [they are examined, we distinguish that their general form is ever}' where the same in the same animal ; that is to say. they are never found oblong in one place and round in another. In nuin tlicy arc rounded. " With rttspect to their size, the globules differ very much in tlie various parts uf the body ; they are smaller in the sul>stancc of tiic Urcr than in the kidneys or ipben. Those of the ner%'ou5 substance are of a smaller size than those of the blood ; the latter arc also larger than those of lymph, of milk, or of chyle. Tlieir number is also vitriablo ; thus there are more in the blood than in chyle or milk. In some soliils they are entirely wanting, as in the cellular tissue, in the fibrous, cartilaginous, and asscous textures. On the contrary, tliey are numerous in the ner'es and muscles. "The colour and chemical composition of the globules, ue generally determined by tho^te of tJie parts in which they arc placed ; this is evident, since Uie latter are formed by the former." 't I- have made this extract, because it presents the opinion of one of Uie first anatomists of Europe ; but it is doubtful if some parts of it are correct, at least they are directly opposed in several respects to t^ careful investigations of M. Milne Edwards,* in * Bechrtdtti MiCTOKOplquM nic h SUqcUir Intime <Ie» Tmiwb Org»- dOUH eta AnimaiH. ExWt ilea Anutn da ScicD. Nat. lifiC The cbMmiiont of Ui. EJwariJt wen ofiginally publwhcd in IlfK). OF THE BOr>Y. France, and to those of Dr. Hodgkin, in Kngland. The fonner thinks that be has establitihed the following lawB : — 1. Thftt the elumentary structure of the following tis- sues is identical in all animals ; viz., the cellular, the fibrous, the vascular, the muscular, and the nervous. 2. That this elementary structure is globular, tlie globules hftinng the same form and the same size, what- ever may be tlie animal or org:an in which the above tissues are examined. He considers these corpuscles to possess a spherical form, each having a diameter of ~ of a millemetre. The observations of Dr. Edwards are the results of such cautious and repeated examinations, that it is scarcely possible to doubt tlieir accuracy. In Uie year following their publication, they were, however, called hi question by Dr. Hodgkin.* This gentlcmim, who has employed a moat perft-ct microscope, constructed by Mr. Lister, denies ttie globular structure of those tis- sues, which ha%'e been supposed by the highest autlio- lilies in these matters, to possess that arrangement in an eminent degree ; for example, the muscular, iktvous, and cellular fibres. I have had sevend opportunities of examining the elementary tissues, by the kindness of my friend Mr. Cooper, lecturer on chemistry, who is in possession of a very excellent microscope. As 1 shall have occasion in tlie subsequent parta of this work, to allude to these observations, it is only necessary to remark in this place, that their general results exactly corres- pond with the statement of Dr. Hodgkin. • AnnaliorPhil.,Aug. 1S27. r OP TUB nuiDS oa humoobs, Section' V. OF THB FLUIDS, OR HUMOURS. Tm fluids 6nt require our attention, on accouol of their importaocc in tJie luumol economy. Tiiey ore contained in the solids, of which they determinu ttie vo- lume, the form, the density, and in general the physical properties. They enter into the formation of every part of the body, howe%*er dense it may appear. They are in most instances