medical essays-第50章
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special arrangements of the vessels and the ducts of all the glands； of the air…tubes and vesicles of the lungs； of the parts which make up the skin and other membranes； all the details of those complex parenchymatous organs which had confounded investigation so long； have been lifted out of the invisible into the sight of all observers。 It is fair to mention here； that we owe a great deal to the art of minute injection； by which we are enabled to trace the smallest vessels in the midst of the tissues where they are distributed。 This is an old artifice of anatomists。 The famous Ruysch； who died a hundred and thirty years ago； showed that each of the viscera has its terminal vessels arranged in its own peculiar way； the same fact which you may see illustrated in Gerber's figures after the minute injections of Berres。 I hope to show you many specimens of this kind in the microscope； the work of English and American hands。 Professor Agassiz allows me also to make use of a very rich collection of injected preparations sent him by Professor Hyrtl； formerly of Prague； now of Vienna； for the proper exhibition of which I had a number of microscopes made expressly； by Mr。 Grunow； during the past season。 All this illustrates what has been done for the elucidation of the intimate details of formation of the organs。
But the great triumph of the microscope as applied to anatomy has been in the resolution of the organs and the tissues into their simple constituent anatomical elements。 It has taken up general anatomy where Bichat left it。 He had succeeded in reducing the structural language of nature to syllables； if you will permit me to use so bold an image。 The microscopic observers who have come after him have analyzed these into letters； as we may call them；the simple elements by the combination of which Nature spells out successively tissues； which are her syllables； organs which are her words； systems which are her chapters； and so goes on from the simple to the complex； until she binds up in one living whole that wondrous volume of power and wisdom which we call the human body。
The alphabet of the organization is so short and simple； that I will risk fatiguing your attention by repeating it； according to the plan I have long adopted。
A。 Cells； either floating； as in the blood； or fixed； like those in the cancellated structure of bone； already referred to。 Very commonly they have undergone a change of figure； most frequently a flattening which reduces them to scales； as in the epidermis and the epithelium。
B。 Simple； translucent； homogeneous solid； such as is found at the back of the cornea； or forming the intercellular substance of cartilage。
C。 The white fibrous element； consisting of very delicate； tenacious threads。 This is the long staple textile substance of the body。 It is to the organism what cotton is pretended to be to our Southern States。 It pervades the whole animal fabric as areolar tissue； which is the universal packing and wrapping material。 It forms the ligaments which bind the whole frame…work together。 It furnishes the sinews； which are the channels of power。 It enfolds every muscle。 It wraps the brain in its hard； insensible folds； and the heart itself beats in a purse that is made of it。
D。 The yellow elastic； fibrous element； the caoutchouc of the animal mechanism； which pulls things back into place； as the India…rubber band shuts the door we have opened。
E。 The striped muscular fibre；the red flesh； which shortens itself in obedience to the will； and thus produces all voluntary active motion。
F。 The unstriped muscular fibre； more properly the fusiform…cell fibre； which carries on the involuntary internal movements。
G。 The nerve…cylinder； a glassy tube； with a pith of some firmness； which conveys sensation to the brain and the principle which induces motion from it。
H。 The nerve…corpuscle； the centre of nervous power。
I。 The mucous tissue； as Virchow calls it； common in embryonic structures； seen in the vitreous humor of the adult。
To these add X； granules； of indeterminate shape and size； Y； for inorganic matters； such as the salts of bone and teeth； and Z； to stand as a symbol of the fluids； and you have the letters of what I have ventured to call the alphabet of the body。
But just as in language certain diphthongs and syllables are frequently recurring； so we have in the body certain secondary and tertiary combinations； which we meet more frequently than the solitary elements of which they are composed。
Thus A B； or a collection of cells united by simple structureless solid； is seen to be extensively employed in the body under the name of cartilage。 Out of this the surfaces of the articulations and the springs of the breathing apparatus are formed。 But when Nature came to the buffers of the spinal column （intervertebral disks） and the washers of the joints （semilunar fibrocartilages of the knee； etc。）； she required more tenacity than common cartilage possessed。 What did she do？ What does man do in a similar case of need？ I need hardly tell you。 The mason lays his bricks in simple mortar。 But the plasterer works some hair into the mortar which he is going to lay in large sheets on the walls。 The children of Israel complained that they had no straw to make their bricks with； though portions of it may still be seen in the crumbling pyramid of Darshour； which they are said to have built。 I visited the old house on Witch Hill in Salem a year or two ago； and there I found the walls coated with clay in which straw was abundantly mingled；the old Judaizing witch… hangers copied the Israelites in a good many things。 The Chinese and the Corsicans blend the fibres of amianthus in their pottery to give it tenacity。 Now to return to Nature。 To make her buffers and washers hold together in the shocks to which they would be subjected； she took common cartilage and mingled the white fibrous tissue with it； to serve the same purpose as the hair in the mortar； the straw in the bricks and in the plaster of the old wall； and the amianthus in the earthen vessels。 Thus we have the combination A B C； or fibro… cartilage。 Again； the bones were once only gristle or cartilage； A B。 To give them solidity they were infiltrated with stone； in the form of salts of lime； an inorganic element； so that bone would be spelt out by the letters A； B； and Y。
If from these organic syllables we proceed to form organic words； we shall find that Nature employs three principal forms； namely； Vessels； Membranes； and Parenchyma； or visceral tissue。 The most complex of them can be resolved into a combination of these few simple anatomical constituents。
Passing for a moment into the domain of PATHOLOGICAL ANATOMY； we find the same elements in morbid growths that we have met with in normal structures。 The pus…corpuscle and the white blood…corpuscle can only be distinguished by tracing them to their origin。 A frequent form of so…called malignant disease proves to be only a collection of altered epithelium…cells。 Even cancer itself has no specific anatomical element； and the diagnosis of a cancerous tumor by the microscope； though tolerably sure under the eye of an expert； is based upon accidental； and not essential points；the crowding together of the elements； the size of the cell…nuclei； and similar variable characters。
Let us turn to PHYSIOLOGY。 The microscope； which has made a new science of the intimate structure of the organs； has at the same time cleared up many uncertainties concerning the mechanism of the special functions。 Up to the time of the living generation of observers； Nature had kept over all her inner workshops the forbidding inscription； No Admittance！ If any prying observer ventured to spy through his magnifying tubes into the mysteries of her glands and canals and fluids； she covered up her work in blinding mists and bewildering halos； as the deities of old concealed their favored heroes in the moment of danger。
Science has at length sifted the turbid light of her lenses； and blanched their delusive rainbows。
Anatomy studies the organism in space。 Physiology studies it also in time。 After the study of form and composition follows close that
