Fig. 303.—A., isolated muscular fibre of a rat, invaded by Trichinella. 510/1. B., section through the muscle of a rat; the infected fibre has lost its transverse striation; its nuclei are enlarged and multiplied. 310/1. C., portion of a Trichinella capsule, at the pole of which connective tissue cells are penetrating the thickened sarcolemma. (After Hertwig-Graham.)
The muscular fibres attacked degenerate, the transverse striation at first disappearing; the fibres then assume a granular appearance, the nuclei multiply and become enlarged, and are surrounded by an area of granular material, which stains more deeply than the remaining contents of the sarcolemma. Two or three weeks after infection, the spirally rolled-up Trichinellæ have grown to 0·8 to 1·0 mm., and in their vicinity the muscular fibre is swollen, spindle-shaped, and the sarcolemma is glassy and thickened. The inflammation also extends to contiguous fibres, especially to the intramuscular tissue, which proliferates greatly, especially in the vicinity of the degenerated fibres. While the latter become more and more absorbed, the capsule is formed by the inflamed connective tissue, which, penetrating into the glassy and thickened sarcolemma from the poles of the spindle, forms the cystic membrane. According to other authorities, the larvæ settle in the intermuscular connective tissue which forms the cyst and not in the muscular fibres within the sarcolemma. The cysts are lemon-shaped and usually lie with their longitudinal axis in the direction of the muscular fibres; on an average they measure 400 µ in length by 250 µ in breadth.
Later on fat cells appear at their poles, and after about six or nine months they commence to calcify, the process starting at the poles (fig. 305). Finally, sometimes after the lapse of years, the captive Trichinellæ themselves become calcified.
Fig. 304.—Calcified Trichinella in the muscular system of a pig; the capsules are not calcified. (After Ostertag.)
