. Anatomischer Anzeiger. Anatomy, Comparative; Anatomy, Comparative. 428 are exceedingly fine, but in some fibers coarser rayofibrillae, which appear to be formed by a fusion of the finer, are seen. They are not confined to the periphery of the bundle as are the coarse myofibrillae („Grenzfibrillen") described by Heidenhain ('00). In cross section (Fig. 1 a) the smooth muscle fibers appear as rounded or oval areas. In the large intestine of the dog, the nucleus is usually at or near the center of the fiber. In Necturus this is not always the case. Very frequently in this form, the nucleus
. Anatomischer Anzeiger. Anatomy, Comparative; Anatomy, Comparative. 428 are exceedingly fine, but in some fibers coarser rayofibrillae, which appear to be formed by a fusion of the finer, are seen. They are not confined to the periphery of the bundle as are the coarse myofibrillae („Grenzfibrillen") described by Heidenhain ('00). In cross section (Fig. 1 a) the smooth muscle fibers appear as rounded or oval areas. In the large intestine of the dog, the nucleus is usually at or near the center of the fiber. In Necturus this is not always the case. Very frequently in this form, the nucleus lies to one side of the bundle, almost independent of the fiber (Figs. 1 and 2). Neither Fig. 1 nor Fig. 2 is magnified sufficiently to show the nuclear relations clearly, however. The nuclei in uncontracted smooth muscle are very much elongated, and show a distinct chromatin reticulum. (Figs. 1 and 5). In none of the forms studied was the chromatin found arranged in a spiral as. Fig. 1. Cross-section of a portion of the intestinal wall of Necturus, entire thick- ness of the serous and muscle coats, the muscle in the resting condition, a longitudinal muscle; b circular muscle; c blood vessel; d mesothelium; e connective tissue; /cross- section of a smooth muscle fiber. Fixation, Zenker's fluid; stain, iron - ha»matoxylin. Leitz obj. 5, oc. 2, drawing reduced ^/g, magnification, 188 diameters. described by Mltnch ('03). Sometimes at the ends of the nuclei a small amount of granular protoplasm can be demonstrated (Fig. 3). Between the anastomosing bundles of myofibrillse is a loose reti- culum of connective tissue. The connective tissue fibrfllie are chiefly intercellular, though in places they pass through the protoplasm of the connective tissue cells, and even occasionally make their way for a short distance in among the myofibrilla3 of the smooth muscle fibers. As will be shown in my paper on the histogenesis of smooth muscle in the pig, this relation is easily understood,
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