Round cells are found in all sarcomata, and are often very small, scarcely distinguishable from lymphatic cells, or white blood corpuscles. Others are larger, and contain an indistinct nucleus, with one or more bright nuclei. The fusiform or spindle-shaped cells are the so-called fibro-plastic cells. They are long, dimly granular, pale bodies, terminating at each end in a fine prolongation. They are slightly granular, and enclose a long, oval nucleus, with or without nucleoli. In size they vary. The giant or mother cells are the largest of human cells, irregular in shape, though usually more or less spherical. They are finely granular, and contain numerous round or oval nuclei, each with one or more bright nucleoli. The intercellular substance exists usually in small quantities. “It may be perfectly fluid and homogeneous, or firmer and granular, or, less frequently, more or less fibrillated. Chemically, it yields albumen, gelatin and mucin.” These growths may occur at any period of life, but are most frequently met with between the twentieth and fortieth year. It is most common in the skin and subcutaneous and intermuscular connective tissues of the extremities. The periosteum and bones, particularly the epiphyses of the long bones and the maxillæ, the female breast, the testicles, and the eye, are also liable to be attacked. They usually arise as nodules, single or multiple, firm or soft, and often attain an enormous size by their characteristic rapidity of growth. They are liable to fatty degeneration, with the production of cyst-like cavities. Calcification, ossification and mucoid degeneration are also common. Sarcomata are decidedly malignant, and are characterized by their rapid growth, their great tendency to extend locally, and to recur after removal, and by their power of reproducing themselves in internal organs. The _Round-celled Sarcoma_, called also from its resemblance in many cases to encephaloid, _medullary_, _encephaloid_ or _soft_ sarcoma, is of a uniform, soft, brain-like consistence, and of a somewhat translucent, greyish, or reddish-white color. The sectional surface, on being scraped, yields a juice rich in cells. It is exceedingly vascular, with the vessels often dilated and varicose. “It can be distinguished from encephaloid cancer by the absence of a fibrous stroma, by the uniformity in the character of its cells, and by the absence of any invasion of the surrounding structure in their growth other than the connective tissue from which they grow.”