We know the nature of their fibres no better than that of those of animal life; but they appear nearly the same under the action of the different reagents. Desiccation, putrefaction, maceration, ebullition, exhibit in them the same phenomena. I have observed upon the subject of this last, that once boiled, the fibres of both systems are much less alterable by the acids sufficiently weakened. After being some time in the sulphuric, the muriatic and nitric diluted with water, they soften a little, but keep their original form, and do not change into that pulp to which raw fibres are always reduced in the same experiment. The last of these acids turns them yellow as before ebullition. I have also made an observation as it respects the horny hardening which is produced the instant ebullition commences; it is this, that it is always the same whatever may have been the antecedent dilatation or contraction of the fibres. The stomach which at death was so dilated as to contain many pints of fluid, is reduced to the same size, all other things being equal, as that which is contracted so as to be no larger than the cœcum. Diseases have a little influence on the horny hardening. The heart of a phthisical patient exhibited to me in the same experiment this phenomenon much less evidently, than that of an apoplectic. The resistance of the organic muscular fibre is in proportion much greater than that of the fibres of the animal muscular system. Whatever may be the distension of the hollow muscles by the fluid which fills them during life, ruptures hardly ever take place in them. The bladder alone sometimes exhibits this phenomenon, which is however very rare in it. In the great retentions of the urine, in which ruptures take place, it is almost always the urethra that is ruptured, and the bladder remains whole. We meet in practice with a hundred fistulas in the perineum, coming from the membranous portion, to one above the pubis. We find in authors many examples of rupture of the diaphragm; we know of but few of the rupture of the stomach, the intestines and the heart. II. _Common Parts in the Organization of the Muscular System of Organic Life._ The cellular texture is in general much more rare in the organic muscles than in the others. The fibres of the heart are in juxta-position, rather than united by this texture. It is a little more evident in the gastric and urinary muscles. It is almost wanting in the womb; thus these muscles are not infiltrated, like the preceding, in dropsies; they never exhibit that fatty state of which we have spoken, and which sometimes loads the fibres. I have not observed in these fibres the yellowish tinge which the others often take, especially in the vertebral depressions.