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The chondrocytes of the epiphysis contain several polysaccharides, not only glycogen, but also proteoglycans (MPS). Therefore the fixation of chondrocytes is difficult. In regard of fixation we must consider, that macromolecules of proteoglycans have a considerable water content (the effective hydrodynamic volume), furthermore the MPS are easily soluble. We examined the preservation of chondrocytes after application of 44 several fixation fluids with the aid of phasecontrast, the electronmicroscope and after staining. The fixation with familiar methods is unsufficient. Consequently we used a double or successive fixation with two different mixtures, once for fixation the proteins (formalin-alcohol-mercuric chloride-acetic acid), another for polysaccharides (LILLIE's alcoholic lead nitrate formalin alternative basic lead acetate). The degree of fixation, the precipitability of the various polysaccharides is quite different and may be characteristic like their staining or solubility feature.

Die Vorstellung der Korrelation von Form und Funktion beherrschte lange Zeit die morphologischen Untersuchungen des Skeletts. Als Funktion wurde die mechanische Leistung angesehen (vgl. Knese, 1970c). Das Skelett ist aber weiterhin ein Ionenpool. Die „funktionelle Gestalt“ist auch in dieser Richtung zu diskutieren. Die Kristallnadeln mit der Grose 25–40 × 200–400 A haben eine relativ grose Austauschoberflache (Robinson, 1964: 100–300 m2/g Mineral; fur den ganzen Menschen 400000 m2; Neuman u. Neuman, 1953). Eine Vergroserung der Kristalle wurde diese Flache verkleinern, eine Verkleinerung die mechanische Leistungsfahigkeit des Knochens einschranken (Knese, 1959 a). Fur die Proteoglykan-(MPS-) Molekule mit ihrer grosen Zahl elektronegativer Gruppen sind dementsprechende Korrelationen anzunehmen.

We studied the modifications of collagen fibrils during the histogenesis of the intervertebral disc of cats. In connexion with these studies it is necessary to distinguish between the fibrillar (functional) structure, the arrangement of fibrils, and the nature of fibrils, their diameter, period and other properties. Collagen fibrils (40--50 nm) of the anulus fibrosus enter in hyaline cartilage and split off in thin fibrils (8--10 nm). In this area the cartilage fibrils have a diameter of 20--22 nm, in a greater distance the diameter is diminished to 7--8 nm. Analogous to the changing of the nature of fibrils, the number of the cells related to the sectional area is diminished. The cells of the anulus fibrosus resemble those of tendons. In the transition area their shape becomes roundish, the number of granular membranes is increased, a voluminous Golgi-Apparatus appears for a short time. Finally, the cells are once transformed in cartilage cells with a small reticulum or cells of fibrocartilage with a capsule and a decreased cytoplasm; some cells are disintegrated. In the capsule of the fibrocartilage cells, parallel orientated filaments exhibit a periodical arrangement. In the border of the capsule, filaments change into periodical fibrils. Therefore, we must regard cells and their surrounding intercellular substance as metabolic unity which in the cartilage may be characterized as the chondron.

The chondrocytes of the metamorphosing cartilage exhibit an extensive granular reticulum, apparently in connection with the increasing intercellular substance and the building of the bearing construction of the cartilage. For a limited time a GOLGI-apparatus appears, which subsequently disappears. Then the cell hypertrophies and an opening zone is built up. By means of the regression of this zone the cavity of ossification center is enlarged. The fibril structure is characterized by a reticular system. In the spaces the proteoglycans are deposited. In compound with the tensile strength of fibrils arise the elastic comprehensive strength of cartilage. The nature of fibrils varied in respect of their diameter (80 to 900 A) and the dimension of their period.

We reported on similar findings concerning the intercellular substances in the early desmal osteogenesis in cattle fetuses and rats and in the intervertebral disc of cats. In 0oth regions fibrils change their structure. In early desmal osteogenesis the bone fibrils are synthetized by osteoblasts, derived from mesenchymal cells. Later the fibrillar structure is lost and substituted by a homogenous substance. Chondroid starlike mineral deposits which are composed of needles appear in the vicinity of the cells. The chondral needles are longer and smaller than those in the bone. Finally the chondral needles are removed by mineraloclasts. During the next step frbrils reappear. They are accompanied by needles in their longitudinal axis. In adult cat the fibrils of intervertebral disc cross directly in bone. The fibrils of fibrocartilage are partly swollen and escorted by starlike mineral deposits. Between the bone fibrils partly amorphous mineral deposits are found generally needle-like along the fibrils. The nucleation of minerals takes place at random. The crystal growth is correlated to the structure and composition of organic intercellular substances and their morphological shape differs correspondingly, being chondroid in the fashion of stars, amorphsus and osseous when in contact and parallel to the fibrils.

The definite articular cartilage originate from 2 anlagen, the primordial tangential layer and the greater part including the joint bone plate from the metamorphosing cartilage. The tangential layer grow by apposition from the perichondrium. Additional the layer becomes also dilatated as a result of the growing volume of the ossification center. In this way the Lamina splendens with residues of cells may be formed. The chondrocytes resemble partly fibroblasts, in older animals possibly even tendocytes. Moreover the cells exhibit a varying different shape. Today it is impossible to interpret the polymorphism of the cells. In the primordial state, the chondrocyts are embedded in a network from thin cartilage fibrils. Later on collagen fibrils from varied thickness (up to 900 A) are formed. The fibrils run only partly parallel to each other, in general they form a network, in which they cross with a low angle. There are great local differences in the fibrillar structure by the same animal.

In this paper we compared the vessels and the surrounding cells in the growing (cattle fetus 520 mm SSL) and metamorphosing cartilage of rats. In the growing cartilage the vessels and sinusoid capillares are accompanied by some morphologic uncharacteristical perivasculare cells which may swell oedematatically. Chondorolytic symptoms appear sporadically but not multinucleated chondroclasts are found. In the metamorphosing cartilage the perivasculare cells grow up to large cells exhibiting an extensive granular reticulum. Firstly the intercellularsubstance seems to be destructed, later on degenerate, they pine away, the chondrocytes as well as the chondrocytes with cyst-like cisternae as such with lacunar cisternae. Also a disintegration of cells occurs. The foci of mineralisation in the neighborhood of the vessels consist of needle-shaped cristals in chains arranged along the fibrils.

In connection with the investigation of the ossification center we discussed the significance of the several sites of osteogenesis. In consideration also of anthropometric relations during growth we got the impression that among others the relations to the muscle- and nerve-system are important for development of bones. The insertions of muscles at the diaphysis are in square dimensions respectively linear, in which regions a tendineous osteogenesis occurs, so that muscle and bones may grow together. The organ of growth for diaphysis is the epiphyseal disk und represents real a diaphyseal disk. Above the epiphyseal disk there remains a part, which acts firstly as growing cartilage. Close to it and partly connected with the epiphysis are apophysis, the points of circumscripted insertions of muscles. In this part a metamorphosis takes place, which in connection of the formation of the cavity of the ossification center formate later on the osseal basis of joint cartilage. With retardation and finally the stop of length growth in epiphysis and metaphysis a new area of bone formation is built up in which the ultimate spongiosa becomes formed. During the formation of the cavity of the ossification center dominate degenerative changings of the cells and intercellular-substances. The chondrocyts accumulate in first easily dissolving carbohydrates. The original meandering endoplasmatic reticulum transforms to small vesicular structures and are fragmentated. The partly roundish and bizarre shaped nuclei shows signs of pyknosis. The cells become a longish dense shape with enclosed vesicles and dense structures, there structural elements cannot be more diagnosed. The fibrills originally arranged in a cross-system decrease in diameter and run now almost parallel. Finally they disintegrate to fragments which are mixed with MPS-granules.

We investigated in continuation of lightmicroscopical (phasecontrast, polarized light) and statistical studies concerning the formation of lamellae and osteons electromicroscopical the nature of fibrils in different areas of the cross section of the metacarpus from a cattle fetus of 520 mm SSL. During the maturation of fibrils in a subperiostal trabecal the diameter of fibrils increased (465 to 470 A). The period (316 or 536 A) contains primarily only a broad band and a small interband. Subsequently the interband increased (221 or 215 A), but the band decreased (324 or 271 A). In the centre of trabeculae the fibrils formate microlamellae. The fibrils split later on in the medial part of the cross section in microfibrils with irregular oreintation and appear lightmicroscopical as intermediate tissue (blasse Mittellinie). At the same time new fibrils are synthesized around the osteocytes and their canaliculi. As the result of a kind of remodeling the fibrils arrange in a parallel order forming packages which appear lightmicroscopical as fibrous felts. These fibrous felts exhibits partly an periodical arrangement with a small band (164 A) and a wide interband (287 A). In a following stage in the fibrous felts lamellae are developed, the length of which increased around the medullary cavity. Firstly after the development of lamellae the definite bone fibrils are reconstituted (diameter: 530 A; band: 348 A; interband: 212 A). Apparently the osteocytes are responsible for these procedures in a stage specific synthetic and lytic activity. The modification of the nature of fibrils results probably after the dissolving of the structural glycoproteins, which stabilize the tropocollagen molecules. A reconstitution of the structural glycoproteins after formation of the lamellae induce the reconstitution of bone specific collagenfibrils. The regulating mechanism for the codification of these structural development are unknown.

We investigated the attachment of tendons to the skeleton (tubercula humeri, patella) in regard to the chondrogenesis and osteogenesis in these areas. Then we compared our findings with those in other sites of skeletogenesis. A metamorphosis, transformation, of structure and nature of cells and intercellular susbstances in correlation with another by feedback characterized the transition from perichondrium and periost or tendon to the skeleton. The initial form of cells are in the case of tendons without doubt the special form of fibrocytes, the tendocytes. We believe that this finding confirm the earlier expressed opinion fibrocytes of the periost with the same structure as tendocytes metamorphose to osteoblasts. The metamorphosis of cells and intercellular substances at tendon attachments occur like in other regions of skeletogenesis (periost, epiphysis) in relative clearly definable stages: tendon, Ansatzstruktur (attachment structure), Ansatzknorpel (attachment cartilage) as a part of apophysis or Einstrahlungsknochen (invading bone). In regard to histogenesis periost and attachment structure are homologous formations. The latter one may be a reticular structure of collagen fibers or a fibrocartilage of which the cells are surrounded from a polysaccharide capsule and a fiber capsule partly accompanied by needle like minerals. The osseous attachment is composed from parallel running fibrils. This structure forms a Grenzstreifen (border sector) with a varied number of needle like crystals along the fibrils. The amount of minerals are increased in the Grenzlinie (border line) to bone and subsequently the crystals disappear. The tendinous mineralisation is a temporary one. However, the fibrils get the Fibrillencharakter (nature of fibrills) of the fibrils of lamellar bone. Later on the bone minerals appear. It is doubtful that osteogenesis occur always in the same manner. However, the vague term ossification can only concern the bone specific metamorphosis of fibrils, never the widely distributed mineralisation. Therefore, skeletogenesis ist one of the metamorphosis stages from the embryonal (!) determinated skeletal mesenchyme to mature and finally to old and atrophying bone. This metamorphosis may be a process probably following a controlled program. A developmental stage releases the development of the next one. A feedback influences the organisation of the different parts, e.g. cells and intercellularsubstances. The increasing diversity of the system developed in the way of Selbstorganisation (self-reproduction). With the exhaustion of the program informations started the ageing.

Das Knorpelgewebe tritt beim Menschen in sehr unterschiedlicher Gestalt auf; eine Reihe weiterer Formen ist bei niederen Chordaten zu beobachten. Ein Teil der knorpeligen Bildungen bleibt zeitlebens erhalten wie Gelenkknorpel, Rippenknorpel, Disci articulares und der Knorpel des Atmungstraktes. An anderen Orten ist das Knorpelgewebe ein sog. transitorisches Gewebe, Vorganger und Platzhalter fur das Knochengewebe. Weitere knorpelige Bildungen erscheinen im Individualleben relativ spat, mitunter nur unter gewissen Bedingungen, z. B. der Knorpel des Callusgewebes.

Die Untersuchungen uber die Mechanik des Skeletsystems haben eine Reihe unterschiedlicher Fragestellungen verfolgt. Sehr umfangreich ist das Schrifttum uber die Gelenk-und Muskelmechanik (Fick, 1904–1911; Strasser, 1908–1917; Steikdler, 1935; Dempster, 1955). Die Form des „normalen“Knochens, die Formanderungen bei bestimmten Erkrankungen, z.B. der Rachitis, und vergleichend-anatomische Beobachtungen fuhrten zu Untersuchungen uber die vermutlichen Beziehungen zwischen Form und Leistung der Skeletelemente. Die mechanischen Eigenschaften des Knochengewebes, seine Festigkeit, wurden dagegen nur von wenigen Autoren untersucht.

Der vorliegende Artikel beschaftigt sich mit einigen Fragen der Struktur des Knochengewebes. Zu dieser Erorterung mus zunachst die Morphologie der Gewebekomponenten, der Kollagenfibrillen, der Interfibrillarsubstanz und der Kristalle dargestellt werden. Schlieslich sind die Fragen der Knochenbildung und der Strukturentstehung zu diskutieren.