The organization of the involuntary muscles is not as uniform as that of the preceding. In these all is exactly similar excepting the differences of the proportion of the fleshy fibres to the tendinous, of the length of the first, of the prominence of the fasciculi, of their assemblage into flat, long or short muscles; in whatever place we examine them, their varieties are in their forms and not in their texture. Here on the contrary, there is in this texture marked differences; the heart compared with the stomach, the intestines with the bladder are sufficient to convince us of this. It is by virtue of these different textures, that the contractility and sensibility vary as we shall see in each muscle, that the force of the contraction is not the same, and that life is different in each, whilst it is uniform in all those of animal life. We shall now consider in a general manner the organization of the involuntary muscles. I. _Texture peculiar to the Organization of the Muscular System of Organic Life._ The organic muscular fibre is in general much finer and more delicate than that of the preceding system; it is not brought into as thick fasciculi. Very red in the heart, it is whitish in the gastric and urinary organs. Besides, this colour varies remarkably. I have observed that sometimes maceration renders it of a deep brown in the intestines. This fibre never has one single direction, like that of the preceding muscles; it is interlaced always, or found in juxta-position in different directions; sometimes it is at a right angle that the fasciculi are cut, as in the longitudinal and circular fibres of the gastric tubes; sometimes it is with angles more or less obtuse or acute, as in the stomach, the bladder, &c. In the heart, this interlacing is such in the ventricles, that it is a true muscular net-work. From these varieties of direction, results an advantage in the motions of these sorts of muscles, which, being all hollow can by contracting diminish according to many diameters the extent of their cavity. Every organic muscular fibre is in general short; those which, like the longitudinal of the œsophagus, the rectum, &c. appear to run a long course, are not continuous; they arise and terminate at short distances, and thus arise and terminate successively in the same direction or line; no one is comparable to those of the sartorius, the gracilis, &c. as it respects length.