Section IV. OP THE HUMAN BODY. (Part 4)

traces of albumen. Tile colouring matter, whatever it is composed of, although Uic least important part of the blood, hai received more attention than either the senim or thfe fibrin. Tliat it is not an essential part of the nutri* tive fluid, is erident by its absence in many trilxM of animals, and by its partial existence in the very high- est. The supply of red blood, however, seems to be necessary to the exercise of the vital functions when these are performed with any degree of ]Jcrfcction ; thus the principal part of the body t)f many species of fishes, receives only colourless fluids ; whilst the heart, the gills, Sec. are nourished by red blood. It is diflieult to aseertain bow the coloured parts are first formed, or of what they actually consi&t, Hewson con- RSD PAHTICLSS. tended, that each is formed of a central solid particle which is contained in a transparent vesicle. He enter- tained some pecrulmr ideas concerning the origin of these two component parts. He supposed that the vesicle was formed in the lymphatic vckscU ; the solid partlclu in the lymphatic glands ; and that tlic red colour vias produced hy the action of the spleen. Sir E. Home and Mr. Bauer, in this country, and Prevost and Dnmas, on the continent, have revived this idea 6f the existence of a solid coq»isclc heing contained in ah erfvelope. Sir E. Home has detected globules la the chyle, sonle of which are as large as those of tlie blood ; he thinks that lliese hodies acquire Ineir red colour by their exposure to the air in the interior of the ptiltnonary organs, where they are changed into the par- ticles of the blood. . According to some recent investigations of Dr. Hodg- Idb, the opinions of Lceuwenhoek, Fontunn, Home, and 6thert, concerning the globular form of the red par- ticles, are altogether erroneous. He also controverts the statements of Hewson, Homo, Prevost, &c., as to the existence of the central globule and the external vesicle ; nor could he perceive the separation of the colouring matter, said to take place by Home and several continental physiologists, in a few seconds after tlic par- ticles have escaped from Ihir body. Instead of being spherical, " the particles of the hunlan blood appear to consist of flattened cukes, whidi, when seen singly, apjjfcar to he nearly, or quite colourless. Their edges are rounded, fend being the thickest part, occasion a depression In the middle, which exists on both surfaces. This form per- fectly agrees with the accurate obsen-ations of Dr. Young, " '* When the blood of man, or of the mammifenc, all of B L 50 8I2B or PARTICLES. which pONMM circular particles, U examined, considerable agitation is at first seen to take place among the particles ; but aH this subsides, they apply themselves to each other bj* their broad surfaces, and fonn piles or rouleaux, which oiftcn agaio combine amongst themselves, the end of one being attached to the side of another, producing ut times Very curious ramifications." 1 have given these extracts from the paper of Dr. Hodgkin, because it appears that his observations are extremely correct. Tbc experiments were made with tlie assistance of a vcr)- powerful and perfect microscope, constructed by Mr. Lister, a gentle- miiri who has paid considerable attention to this subject. Through the kindness of thcM: gentlemen, I have had an opportunity of examining the human blood with this instrument, and my obser'ation entirely confirmed tliat of Dr. Hodgkin, excepting that I thought a central cor- puscle miglit be detected. The size of the particle iias been very differently esti- nuted. It is very minute, which probably will account for tlic diticrepHricies that exist in the following measure' mcnts. The diameter, according to Jurine, is ^ part of an inch, Ditto, in a second measurement, ^ — Bauer, without colouring matter, ^ — Bauer, with it ' — Wooluston j^ — Young ^ — Kftti^r ^ — IVevost and Dumas • • ■ • «^ — Ho<lgkin j^ — • COLOUR AND SPECIFIC GRAVITY. The size certainly varies in different animals, being largest in fishes and smallest in man and the mammalia. The magnitude does not depend on the relative bulk of the body, for, according to I^ecuwenhoek, the particles arc not larger in a whale than in the smallest fish. The colour of the particles, which is red, has been attributed to various causes. It has been ascertained by Bcrzclius, that tht! particles contain a proportion of the red oxide of iron, and tliis substance has been, in con- sequence, very generally considered as the cause of the colouration. Berzelhis himself, and also Brande, Pre- rost, and others, do not conceive Uiat the colour of the blood depends on the iron which it contains, but on a peculiar animal dye or jelly. Whatever be the nature of the colouring matter, it is certain that the action of the atmospheric air is necessary to its production. I have often perfonncd the experiment of exposing a portion <if diyle, recently taken from a dog, to the influence of the air, and I have always seen that the chyle loses its milky appearance, and gradually assumes a rosy tint on its Gurfaco. ' The specific gravity of the particles exceeds that of the other constituents of the blood ; it is thus known that the former sink into the lower part of the crassa- mentum. • The (juantity has not been very accurately ascertained ; Heraelius calculated that the partick-s formed sixt)'-lbur parts of the crassameutum in the hundred. The chemical properties of tliese bodies have occupied considerable attention, but the results are not satisfac-' tory. Berzeiius, Fourcrny, and others, thought they could detect a quantity of the red oxide of iron. Mr. B 3 CHEMICAL PR0PERTI8S. Brando detected a minute quantity of iron in the aslies of the «.Tum and tibrin as well us in those of the red glo- bules ; but he supposed that the red tint is produced by u peculiar animal mutter. Wells altogether denied the existence of iron. The question appears to be decided hy Dr. Engelhart,* in favour of Uie opinion of Berr^elius. lie has detected the per oxide of iron in the proportion of n half per cent. ; it is confined to the particles, its presence not being indicated either in the serum or fibrin. Tlie colouring matter, when incinerated, leaves the 80th part of its weight of ashes, consisting, occord- ing to Berzelius, of — oxide of iron, 50'0 ; subphoKphale of iron, 7'5 ; phosphate of lime, with traces of magnesia, 6'0 ; pure lime, 20'0; carbonic acid and loss, 16'&>— 1000.. ! have now concluded the general description of the properties of the blood. Thi& ha-s occupied, perhaps, more space than should have been allotted to it ; hut I am so strongly impressed with the conviction, that a knowledge of the circulating fluid is indispen-sable to every one who studios the human organization, that I have extended these observations beyond the limits which 1 had first proposed. The third class of fluids, vli. those which proceed from the blood, are so numerous and di^'ersified, tliat it would exceed the limits of this work to inv&stigate each separately. This is tlie less necessary, because many of the humours will be afterwards considered witli the structures in which they are produced. Tlie fluids of which I am s|>eaking, are all derived from the blood i ■ Tutno, El. of Chenulry, p. 7iS. L.i 3 SBCBKTED FLUIDS. 53 tht mo(t« 'of separation, however, varying ntcording to tin.- kind of instruinculs by which it is effcctirti. The' to-m of aeeretioR is applied to the process by which the fluids nre detached from the blood, and these ore, in consetiui'iice, often called the secretion:<. The secretory organs, different as they are in their structure and ap-' pcarance, all consist essentially of the blood-vessels, which bring to them the materials for secretion, and of the pecidiar canals which receive the secreted fluid.' There are tlirue species of secreting bodies. 1. Exha- lent arteries. 2. Follicles. 3. Glands. In the first, the fluid exhales, or transudes from the extremilies of the minute vessels. In the second, the humour is supa- rated in a small bag or follicle. In the third, the struc- ture i& much more complicated ; it is indeed so intricate, that at the present time it is but very imperfectly known. The character of the secreted fluid is influenced by the' Dature of its secreting organ ; ttius tlic exhalations are the simplest in their chemical properties ; whilst the glandular fluids are extremely compound. The first class is subilivided into those perspired fluids, which, having been sei)arated from the blooci, are again received into the system through the medium of the lymphatics; and into those which, on being dotuclied from the circulating mass, arc directly discharged from the body. The first are called rccrcmcntitial, the second, excrementitial, exhided fluids. \ , The follicular secretions resemble each t>ther iiTiJeing formed in follicles, and in being excrcmentitious. The last class of fluids are elaborated in the compli- cated organs, csillcd glands. These bodies are very in- tricate in their structure, and the fluids which are formed by them, are also extremely compound. OF TUB LYHPU. The lymph is the transparent liquid which is returned to the blood by the lymphRlic vessels, M. Magendie has well observed, that nothing more strongly proves the imperfection of our knowledge concerning the function of absorption, than the ideas of physiologists about the lymph. This name has been variously applied to the fibrin, and to tiie serum of the blood ; to the fluid of the serous inembmnes, and to tlie vxlialutioa of the cellular tissue. Willi Uie information wc povscse at pre>>ent, it is impossible to decide, if the fluids se- creted by the serous and cellular membranes are iden- tical with the contents of the absorbent vessels. In this uncertainty, 1 shall restrict the name of ])-mph to the liquid contained in the lymphatics. The lymph has a saltish taste, and a strong spermatic odour. It is usually transparent and colourk-ss, but, ac- cording to Mageiidie, it has, when 6rst removed from its vessels, a slight rose-colour ; occasionally it presents a light yellow tinge, and at otijer times a red madder colour. The specific gravity, compared to that of distilled water, is as 102228 to 100000. A\Tien extracted from its vessels, the lymph soon con- geals. Its rose-colour becomes more deep, and an im- mense number of irrcgidar reddish fitoinonts an: deve- loped, which are very analogous in appearance to the vei>- seLs spreatl in the tissue of the organs. When the masa of the lymph thus cimgidated, is examined carefully, it is found to be composed of two parts ; the ope solid and forming a great many cells, in wliich the other re- mains in a liquid state. If the solid part be separated, the liquid congeals again. The former has much ana- logy to the crossauientuin of the blood, and becomes op TUB SOLIDS. scarlet red by the contact of oxygen gus, and purple when plungfd iu carbonic acid.* The composition of the lymph must vary at different times as the absorbents take wp such heterogeneous sub- stances. The following is the analysis made by M. Chevreiil ; the lymph examined wjis that of a dog: — Water 926"4 Fibrin 4-2 Albumen 61-0 Muriate of Soda 61 Carbonate of Soda I'S PhoBphate of Lime .... J ITiosphate of Magnesia . . > 0"5 Carbonate of Lime . . . ; 10000 Sectcon VI. OF THE SOLIDS. The Solids, which constitute the basis of the body, deturminc its form and proportions, and impress ijjmn it those niovcmcnts which are so strongly cbaraeterislic of animal existence : tlicy also contain and act upon the humours, so as to put them into motion. They are generally distinguished by the name of organs ; but some writers have judiciously termed them instruments, on account of the actions they txercise. The solids fonn but a small proportion of the entire * MagcDiJic Coni|ieii of Pliv. p. 307. ^ 56 FORM AND COLOUB OF SOLIDS. body, when considered abstructodly. It has already been stated, that their weight is generally six, tight, or even ten times less than l;hiit of the fluirk. From this it is evident, that, in every oignn which may, on a slight ex- anunation, appear to be entirely solid, there is a very large proportion of fluid matlcr. The form of the solids is extremely variable ; it b generally more or less rounded, and consequently the lines are not straight, nor the aisles perfect In the greater part of the organs, the length considerably ex- ceeds tlieir breadth and thickness ; there are but few in which the tJiree dimensions are nearly equal. The form in which length predominates, is called the fibrous; whilst the term of laminated or membranous, applies to that in which the length and breiidth arc more or less of equal extent. In some organs, the particles are not arranged in any regular order, but are formed into small grains, which, united together, produce an evident gra- nular disposition. The fibrous form is met with in many parts, for instance, in the muscles, nen-es, liga-; mcnts, bones, &c. The membranous form is also fre-r quently obsen'ed, a.H hi the serous, mucous, and other mcmbmnes. The granular form belongs more espe- cially to the viscera ; it is very evident in the liver, in the pancreas, and so forth. The colour of the organs is as variable as their form. Some arc brown ; others are red, yellow, or wliite, Most of tbem are opaque, a few only of the inort deli- cikte structures being transparent. Their degree of co? hesion is extremely different ; some are so soft, that it is witli difficulty they can be examined ; others agaio, are so Arm and resisting, that considerable efforts ore requirt>d in order to break them. Most of tlie solid^ TKXTURK OF SOLIDS. are flexible, compressible, extensible, and elastic ; Kome,, on the contrary, are nearly, if not entirely, inextensible and incompressible. Tliose properties relatipi* to the colour and cohesion of the solid organs, principally depend upon llic fluids they contain. This is proved by observing the effects of desiccation ; if n ligiiraent is sutRcienlly dried, it be-, cornea transparent ami very clastic ; whilst in its natural state, it is opacjue and inelastic. Other, and equally marked changes, are produced by the loss of the fluids in the muscle.s, nerve-s, membranes, &c. The interior arrangement presents numerous vuria^. lions. Many organs are hollowed so as to form canals and reservoirs, which have external communications, such as the alimentary canal, and the urinary bladder ; otiiers form cavities, which are entirely closed ; the serou^ apd synovial membranes are of this order ; others agiun . constitute closed canals, which have ramifications ; these are called vessels ; lastly, some arc solid or full, as the . livpr, the spleen, &c. The intimate composition or texture of the solids i& extremely complex in the higher classes of animals, and in man. Although this branch of anatomy has alway& commanded great attention, it is only within a very re- cent period tliat correct ideas have been entertained of the nature and arrangement of the organic solids. Each of these is composed of fdaments and laminBC, which arc interlaced with each other so as to form a kind of net-work, in the areola and cells of which, the humours arc contained. Tiiis combination of fluid and solid parts is %-ery intricate, and is essential to the exercise of those _ operations, on the continuance of which, life depends. ' )t is necessan', in order to obtain an accurate knowledge ELRMKNTARY FIBRES. of the Rtructure of the body, to investigate the exact na- ture of these solid elements. The ancients supposed that cvcr^- solid organ might be reduced by a species of anatomical analysis, to a simple fibre, vrhicli they called tlie elementary fibre. They said, that this wa.s every where of the same nature, and that it was formed of earth, oil, and iron. They also imagined, that tliis fibre produced what we term the eel- lulnr tissue; and that this tissue, under different dejn'ees of condensation, formed the various organs of the body. Hullcr, who admitted the existence of the elementary fibre, thought that it was not visible, and that it could only Ik; distinguished by the mind ; being to the anntomist, wliat Uio line is to the geometrician. This opinion is evidently erroneous, as matter must have existence. It is equally incorrect, at least in man and in the superior animals, to imagine that the cellular tissue forms the basis of all the solids. Hiis tissue is, undoubtedly, the most extended element in the animal organization ; but it is jiot the only one. The best anatomists of the pns sent day are agreed, that there are at least three, if not four, elementary fibres; viz. the cellular, the muscular, and the nervous. This divinon, which was suggested by Hallcr and adopted by Blumenbach, has been mo- dified by Professor Chftussicr,* who contends, that there is a fourth fibre, which he calls Ibc albugineous. Many distinguished authorities, in whose opinion I concur, believe tliis to be merely a condensed modification of the cellular fibre. Tlie cellular, the muscular, and the nervous, are re- garded tm the elemcntjiry fibres, because we cannot, tfith ■ Ti1)k Sya. do Selito Ofguiuiue*. PROPBRTIBS OF CBLLULAB FIBRE. our present means of analysis, reduce any of them to more simple structures ; luid because there is no living creature with which we are acquainted that presents any others in its composition. These three elementary fibres arc not met with in every animal ;