Section IV. OP THE HUMAN BODY. (Part 5)

there are many species in which nothing can he distinctly detected, except the cellular substance, and others which have only the cellu- lar and the muscular, without the nervous fibre. The cellular fibre, the most essential to organization, since it exists in every animal being, consists, according to some observers, of minute particles ; while others re- gard it as bi'inf^ formed of a condensed animal substance devoid of globules, tliat which Meckel calls, the coa- gulahle matter, and which we have previously described.* I have fretjuently examined the cellular membrane with the assistance of the microscope ; the fibres which arc very distinct, do not appear to be composed of globules, although globular bodies are seen at irregular distances, either singly or clustered together, but never presenting a linear arrangement. This fibre is capable of great extension, and is highly clastic. Its colour is a grejnsh white. It neither possesses animal sensibility nor con- tractility. Fourcroy, who is so celebrated for his suc- cessful researches in the department of animal chemistry, thought that the cellular substance was composed of gelatine ; but wc Icarn from the experiments of Mr. Ilatchett, that it consists principally of coagulated albu- men. Dr. Bostock states, however, that membranous matter also contains jelly and animal mucus. The muscular fibre is not such an extended element as the last, OS tliere are many animals in whicli no traces of • Sm p. 25. M MUSCULAB AND XKKVOUS riBRES. it can be distinguished. It appears to consist of a deli- cate ^tieath of coUular tissue, and of a peculiar substance whicb b contained witbin it. Sir E. Home, Mr. Bauer, and r}therB, thougbt they had proved that tbe fibre was globular ; and this was g:enera]ly believed till some doubts weru thrown on the theorj- by Dr. Hodgkin, wbt) denies the existence of particles in the muscular stnio ture. I have made several microscopical observations upon this fibre, and I have noticed a great number of dclicute lines marking it inmswrscly, but no globules. This appearance was discovered by Dr. Hodgkin and Mr. Lister ; and as they ha'e not detected it in any other tissue, they regard it hr the distinguishing feature of muscle. The fibre is soft and extensible, but it has little elasticity. The colour, which is rather variable, IK io man gcncriUly reddish-bpown. Tlie pnjperty which so strongly characterizes this fibre, and concerning the nnture of which there has been so much discus.sion among physiologists, was termed by Ilaller, irritability. I prufcr the expression of muscular conlractilit)-. be- cause it at once expresses the nature of the property, and cannot l>c confounded with any other physical or moral phenomenon. This property, which is resident in the muscular fibre, requires for its development tlte applicntion of a stimulant, wliich may be mechanicnl, cliemical, or vitjd. The analyses which have been made, shew thut this fibre consists principally of fibrin. The nervous fibre, the least extensive of the three in its formation is somewhat similar to the last ; that is to say, it consiKts of a sheath or tube of cellular mem- brane, in which is lodged the medulla or pulp, peculiar to the nervous systpm. Minute inspection seems lo prove that Uterc are no globules in the fibres, but a few AI.nUGINE0U3 FlItSR. mny be seen irregularly intcrspiTst-d between tlicm. It is impoHsibte to dUtinguuih the exiict oatvirc of these globules. This fibre is soft und dchcHte, and of a whitish colour. It is distinjruUhed from itll other sub- stances by its peculiar property of transmitting impres- sions to the sensorium, and of conveying the influftice of volition from Uie brain to the yolunlar)" mnscles. Il is composed of water, olbumeu, a peculiar fatty sub- staut-e, osmazome, phosphorus, und some sails. With respect to the albugineous fibre of Chnu.'fflicr, it forms the basis of the fibrtjus and ligamentous tex- tures. It is extremely resistant, and nearly, if not quite, iuelaatic. The colour is ven,' white, and it has a satiny appearance. It is insensible, and posfiesses no contrac- tility. The principal properties of this fibre depend on its great strength and resistance, which enable it to ftillil itsotlicc in the economy, viz. that of tying and binding parts together. Its chemical qualities are nearly the same as those of the cellular membrane. 1 have already stated, that most anatomists consider this fibre to be merely a condensed modification of the cellular, and a careful examination of it proves the cor- rectness of this opinion. In order to ascertain how far the two substances resembled each other, I placed some pieces of ligament, of fascia, and of tendon, which are all formed of the albugineous fibre, in maceration. In the course of about three months, I found that they were reduced into a soft, pulpy kind of cellular mem- brane, having precisely the same appearance as the Iattcr,> when that is treated iu the same manner. From these and other obsen-ations, 1 have no doubt that the albu-^ gineoiis fibre ought to be enumerated as a product of thfi>' cellular, and not as an elementary structure. 63 CLASSIFICATION OP TUB OHGAKS. Having pointed out the priacipal properties of Uic vlc- mentarj- (ibros, I shull in the next placo proceed to the coiusideratiun of the compound solids which are pro- duced by their union and combination. The ancients diridnd the organs of the body into similar and dissiiniltir ports. The first clnss consist:^ of those organs which ^n: similar to or resemble each other ; Huch as the bones, the muscles, the nen'es, &c. The second clans is composed of the union of dissimilar ports ; thus the hand is a dissimilar part, which con- sists of several organs, as bones, muscles, nerves, &c. : and so also with respect to tlie organs of the senses, of digestion, &c. This arrongemciit, modified and im- proved, has been the origin of all xubsecjuent classifica- tions. It has thus been of great service, and, so far as it extends, it is well fotmded. But it is not sufficiently minute to be of imy practical use ; for we find, that there arc several different structures united in the same or^n, which it is desirable to separate and to examine individually. For instance, in one of ttie simitar parts, a bone ; there is, first, the animal portion, which con- tains the earthy matter. 2. The vessels. 3. The ner'es. 4. The medullary membrane and the marrow ; and, lastly, there is the periosteum. In the same manner a muscle consists of the musculcu* fibre, of cellular tissue, of vessels, of nen'es, and of tendon. A most important modification in the mode of inves- tigating the composition of the animal body, began to prevail soon after the middle of the hist century. At this period, se%'eral writers pointed out the resemblance and connexions that exist between cerUiin membranes and other piu^s, which previously had been regarded only as so many insulated and independent structures. BONN — SMmi — PIN EL. One of the earliest of tiiesc authors, is Andrew Bonn, who, in a thesis published in 1763, entitled " De Con- tinuationibus Membraniinun," made several important obscrvalioas, the credit of which hiis been generally attributed to his successors, and especially to Bichat.* Some years afterwards, the necessity of attending _to the tissues of the different organs, was illustrated in an exccltcul paper ou Inflammation, wliich wus read by Dr. Cannichuel Smyth, in tlie year 1788.t He states, that after a careful consideration of the various furms of in- flammation, he waf> induced to believe that the prin- cipal causes of the specific distinctions they exhibit, de- pend upon the natural texture and functions of the part inflamed. He Uien proceeds to shew, in a most satis- factory manner, that when inflammation attacks the skin, the cellular membrane, the serous membranes, the mu- cous membranes, or the muscular fibres, it is in each in- stance distinguished by peculiar characters, and that these characters are always similar in the inflammation of the different parts which are respectively formed by the above tissues. An example of this philosophic mode of tjluciclating the phenomena of disease, is ofturded in the inflammation of the mucous membranes, which is marked by the same leading symptoms, and has the same termination, whether it occurs in the mucous mem- brane of tlie eye, of the throat, of the bronchi, or of the alimentary canal. This appears to have been the first attempt to arrange the symptoms of inflammation according to the tissue of the organ in which the disease occurs. About Uie same time, Pinel adopted nearly a similar method of distin- • MagvuJii'. Comp. of I'liy. Noli- by lit. Millisan, p. 528. t Medical CommuDicatioiU, vol. U. p. IfrtI, tt k;. IMPOBTANCB OF CLASSIFICATION. giitiihing dlseaiK^s according to the structuru of the or- ganic solids.* There is, perhaps, no event in modern times, that has had so greftt and so beneficial an influence on the prac- tice of medicine, as this improvement in the manner of cujlivaling human anatomy. It has led medical men to remark the great similarity which exists in the cbaritc- ters of diseases of similar textures, howe^-er distantly these may be placed from each other. It has afforded to the [lAthologist an incalculable advantage, in investi- gating tlic nature of disease ; it has enabled him to tract* the changes which are induced by it ; to compare thes<* morbid results with the healthy structure ; and, lastly, to ascertain those general laws which are Uie only ra- tional bases on which the practitioner can fonnd his diagnosis and treatment. It is to the knowledge of structure which wc now possess, that ought to lie attri- buted the ]>n)duction of the many excellent works which have been published, within a vtry few years, concern- ing the nature and effects of disease ; and to tlic same' source, may in a great degree be referred the simplicity and success which mark tlic practice of medicine in the' present day. Tlie method of studying the anatomy of the body, according to the intimate structure of its organs, has had an equally adranUigeous effect on zoology. The' most enlightened naturalists, adopting the scientific' system nf M. Gcoffroy St. Hilliire, no longer rest their divisions and classes on llie external form, or even on the fijnclions of the various parts of the animal ceo-' nomy, but npon the more essential and determined peculiarities of internal structure. * NoMgnrphK PhilcMpt), l7Sa. CLASSIFICATION OF BICHAT. The ideas of Bonn, Smyth, and Piad, were seized by Bidut, who, on this slight foundation, produced a history of the coraposilion of tliu humun body, which is one of the most important works that has ever appeared reUti^'e to medical science. This illustrious man, en^ doweii with a genius worthy of the task which he undertook, devoted himself with almost unparalleled patience, to the minute investigation of our corportial frame. Provided with means of observation, which a^ipcar almost incredible in a country where crery con-' wivablc obstacle is opposed to the practical cultivation of anatomy, Bichut sacrificed every thing to the ad- vancement of the great work in which be was engaged. We may form some notion of his ardour and industry from the simple fact, that, in tlic short space of six months, he personally examined more tlian six hundred dead bodies.* The product of so much research was deser^nog of the talent and labour which had been be- slowed upon it. The Anatomie G^n^ralc has been received throughout Europe as the very foundation of the branch of knowledge upon which it treats; and will remain a lasting memorial of u man, who was unhappily too soon lost to the science of wliich he was one of th« brightest ornaments. Id the above work the organic solids are reduced to a certain number of elements, which are called timptt tissuea. A tissue is not, strictly speaking, an clement, but a congeries of fibres ; as it forms, liowever, the basis of all other parts, it may stilt be regarded as an ana- tomical element. Thqse tissues consist of the following: — I. The ceU * Notice Ri>toriqu« fur Bichtt, ptcfind la Maing^ult'i odilioii of Uio G«i>:nl Analomy. r CLASSIFICATION lular ; 2. The nervous of animal life ; 3. The nervous of organic life ; 4. The arterial ; 5. The venous ; G. The ezhalant; ?• The absorbent, with its glands; 8. Tbe osseous; 9. The medullary; 10. The cartilaginous; II. The fibrous; 12. The 6bro-cartilapnous ; 13. The muscular of animal life ; 14. The muscular of organic life; 15. The mucous; 1 6. The serous ; IT-Thesyno- vial; 18. The glandular; 19. The dermoid ; 20. The epidermoid ; 21. The pilous.* These he divided into gcnenJ and particular tissues. The first arc called general tissues, because they are more generally distri- buted than tlie second. Bichat also called them gene- rating tissues, because they concur in the formation of all other parts ; they consist of the oJlular, the nervous of animal life, the nen'ous of organic life, the arterial, the venous, the exhalant, and the absorbent. The whole of these do not necessarily enter into the composition of every organ, but some of them are always observed. The cellular, the exhutaot, and the absorbent systems are met with everywhere, for tlicy arc the agents of the compwiition and nutrition of all living beings. Arteries and veins, or at least vessels which carry red blood, are deficient in many parts, as in cartilage. The nerx-es are yet more confined than the blood-vessels, as there are many organs in which they cannot be traced. It must always be recollected, that these generating systems are only independent of each other in u limited degree, as there is a mutual connexion between them, each assist- ing in the formation of tite other. For example, the cellular tissue is penetrated by vessels and nervea ; the VeueU contain cellular membrane and nerves, and they * Aml Gca. ion. i. p. as. OF BICnAT. I even receive other vessels in their parietes. Again, the ncrv«s have cellular texture which forms sheaths for their libns, and blood-vessels by which they are nou- rished. The particular systems which are derived from the former, consist of the osseous ; the medullary ; the car- tilajrinous ; tlie fibrous ; the fibro-cartilaginous ; the mus- cular of animal life ; the muscular of organic life ; the mucous ; the serous ; the synovial ; the glandular ; the dermoid ; the epidermoid ; and the pilous. The diffe- rent tissues which wo have unumcrHtcd, general and particular, are joined with each oilier in various propor- tions to form the solid organs of the body, llms, a bone is an organ, composed of several tissues : of the osseous, which constitutes its substance ; of the mediUlary, which is contained in its interior ; and of the fibrous, which affords it an external envelope, under the name of periosteum ; lastly, each of these tissues possesses its proper cellular membrane, vessels, and nerves. The organs which arc produced by the ujiion of acve. ral tissues, in tlicir turn lurc associated together so as to form what is termed an apparatus ; tlic different parts of which, although their situation, structure, and even peculiar action may be very distinct, still concur in the accomplishment of one common function. Thus the teeth, the salivary glands, the stomach, the intestines, and the liver, form the apparatus of digestion. I have given rather a detailed account of the arrange* rocnt of Bichat, because it is so excellent in itself, aod also, because it is the basis on wlucb nil the more recent classifications are founded. There are, however, certain parts of it which admit of improvement, and in coBse* f2 I MODiriCATION or THB qtwniie of this, .lome alteratioDs h*ve b«en mad« h^ ■Cvcral celebrated anatomists. I shall state thosu which appear to be required. First, wc should include unda the general term of vascular tissue, the cxholant, the absorb- ent, the arterial, and the venous, because thcr are only slight modiiicalions of the same stnicture. It is also ne- cessary to add to the vascular sj-stem, a peculiar tissue, which haR been long known to anatomists, altlKnigli its proper character has only recently been determined ; it is at present distinguished by the name of the erectile tissue. The nervous system of animal life, and the nervous system of organic life, belong to the same tis- sue, viz. the nervous. The medullary tissue is only a part of the adipose. The fibro-cartila^nous and fibrous organs are modifications of the same structure, viz. the fibrous. The muscular system of organic life is princi- pally distinguished from the muscular system of animlil life, by the difference in the disposition of its fibres and in the mode acconting to which they arc excited to con- tract. Tlie sj'novial tissue is a part of the serous ; the dermoid system is a condensed variety of the ceUular membrane ; lastly, the pilous and epidermoid texturca belong to the same class. There is much uncertainty as to the nature of thtf epidermoid texture. Many anatomists regard it aa aa inorganic substance which is concreted on the external surface of the i)ody. Beclurd says, that it is almost inorganic, being the product of excretion, and that it ought not to be considered as an anatomical clement ; that it contains no distinct cellular structure ; that by maceration it is reduced into a kind of mucilage, and that chemistrj' demonstrates in it albumen according to CLASSIFICATION OF BICIIAT. some, or mucus according to others. NotmllistaiHling this opinion, I believe [hat the epidermis is an organized sulistance, and that it is a product of the ceUular texture. The reason-s for this belief will be stated in the chapter on the Skin. The epidermoid tissue