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LECTURE Y.

FEBRUARY 27, 1858.

NUTRITION, AND CONVEYANCE OF THE NUTRITIVE JUICES.

Tendons.—Cornea.—Umbilical cord.

Elastic tissue.—Corium.

Loose connective tissue.—Tunica dartos.

Importance of cells in the special distribution of the nutritive juices.

Allow me, gentlemen, as a supplement to what we saw and discussed in the preceding lecture, to lay before you a few more preparations in illustration of that peculiar species of nutritive arrangement which we have already seen to exist in various tissues, and which, I hope, will appear to you of very great importance in pathological processes also.

You will remember that the last object of our consideration was a ligamentous disc (Bandscheibe), as it occurs in its most marked form in the knee-joint in the so-called semilunar cartilages, which are really no cartilages at all. On the contrary, they possess the qualities of a flat tendon, and the individual structural relations which we found in them, are repeated throughout the whole of the transverse section of a tendon.

We have to-day a series of objects from the tendo Achillis, both of the adult and the child, displaying the different stages of its development; and as this is, moreover, a tendon which is of importance in more than one way in an operative point of view, I may, I am sure, be excused for speaking a little more at length concerning it.

On the surface of a tendon we see, as you well know, with the naked eye, a series of parallel, whitish striae which run pretty close to one another in a longitudinal direction, and give rise to the characteristic glossy appearance. In a microscopical longitudinal section these striae lie farther apart, so that the tendon presents a somewhat fasciculated appearance and looks less homogeneous than on the surface. This becomes much more evident in a transverse section, in

Fig. 37.

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Fig. 37. Transverse section from the tendo Achillis of an adult. From the sheath of the tendon, septa are seen at a, J, and r, running inwardly, and uniting into a network so as to form the boundaries of the primary and secondary fasciculi. The larger ones (a and b) generally contain vessels, the smaller ones (e) do not. Within the secondary fasciculi is seen the delicate network formed by the tendon-corpuscles (reticulating cells—Xetzzellen), or the intermediate system of juice conveying canals (Saftkanalsystem). SO diameters. TENDONS. 91

which a series of smaller and larger divisions (bundles, fasciculi) are offered to the view. On magnifying the object, an internal arrangement is shown almost exactly corresponding to that which we have observed in the semi-lunar cartilages. Externally, the tendon is invested in its whole circumference by a fibrous mass, in which the vessels are contained, that are entwined around the tendon. From these at different points vessels proceed into the interior, where they are to be seen in the larger partitions which separate the fasciculi (Fig. 37, a); but into the interior of the fasciculi themselves no trace of a vessel enters, any more than it does into the interior of the semi-lunar cartilages; there, on the contrary, we again meet with the network of cells we have been talking about, or, in other words, the peculiar system of juice-conveying canals of which we lately considered the import in bone.

Tendons may therefore in the first place be divided into larger (primary) bundles, and these in their turn into a certain number of smaller (secondary) fasciculi, which are separated by broadish bands of a fibrous substance containing vessels and fibre-cells, so that a transverse section of a tendon presents a meshed appearance. From this intervening substance, which must not, however, be regarded as a tissue of a peculiar description, there pass into the interior of the fasciculi stellate cells (tendon-corpuscles) which anastomose with another and establish a communication between the external vascular, and the internal non-vascular, parts of the fasciculi. This relation is, of course, much more evident in the tendons of children than in those of adults. The older the parts become, namely, the larger and finer do the processes of the cells in general become, so that in many sections we do not meet with the real bodies of the cells, but only sec minute specks, which, by altering the focus, may be traced into filaments—or point-like orifices. The individual cells, therefore, come to be more widely separated, and it becomes more and more difficult to obtain a view of the whole of a cell at once. Besides, we must first obtain a clear notion of the relation between a longitudinal

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and a transverse section. Where, namely, in a longitudinal section, there are spindle-shaped cells, in a transverse section will be seen stellate ones, and to the network of cells displayed in the transverse section corresponds the regular succession of spindle-shaped corpuscles, arranged in rows which we see in a longitudinal section, entirely in correspondence with the plan which we have shown to be followed in connective tissue. The cells, therefore, are here also only apparently simply spindle-shaped, when an exactly longitudinal section is examined; but if it has been made a little obliquely, the lateral processes are perceived, by

Fig. 38. Transverse section from the interior of the tendo Achillis of a new-born child, a. The intervening mass which separates the secondary fasciculi (corresponding to Fig. 37, c), and entirely composed of densely aggregated spindle-shaped cells. Directly anastomosing with these, we see on both sides at b, b, reticulating and spindle-shaped cells running into the interior of the fasciculi. 300 diameters.

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means of which' the cells of one row communicate with those of another.

F;g. 39.

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Up to the present moment the progress of the growth of tendons after birth has not been made the subject of a regular investigation, and it is unknown whether any further multiplication of the cells takes place in them; this much, however, is certain, that the cells in many places afterwards become much elongated, and the intervals between the individual nuclei extremely great. The actual structural relations, however, do not thereby experience any change; the original cells also continue members of the great system of tubes, which in the perfectly developed tendon pervades the whole tissue. Hence we see how,

Fig. 39. Longitudinal section from the interior of the tendo Achillis of a new-born child, a, a, a. Intervening bands. b, b. Fasciculi. In both we see spindle-shaped, nucleated cells, partially anastomosing, with an inter-ccllular substance slightly striated in a longitudinal direction, the cells being more crowded in the bands, and less numerous in the fasciculi.. c. Section of an interstitial blood-vessel. 250 diameters.

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