_Thoracic cavity._ Having accomplished the examination above described, we may proceed to expose the cavities of the thorax and abdomen, in the manner already explained, (_vol._ iii, _p._ 52) remembering always that, by carelessly wounding the thoracic viscera, we shall, in a great degree, defeat the objects of the dissection; on this account it will be advisable to make the division of the ribs with scissars, instead of a scalpel. From the examination of these cavities we shall, in the first place, derive a confirmation, or refutation, of the opinion respecting the maturity, or _viabilité_ of the subject, which the external view of the body had suggested. Previous to the end of the seventh month the heart will be found exceeding in size its just proportions, and without much difference of capacity between the auricles and ventricles. The lungs will appear small, solid, and retracted from the anterior part of the cavity. In the abdomen we shall find the liver very considerable in size, and situated near the umbilicus, from which it afterwards gradually recedes as the fœtus advances. The gall-bladder will be found to contain a nearly colourless serous fluid, which during the eighth month gradually becomes yellowish, and acquires a bitter taste. If the appearances above described be compared with those which are displayed on the dissection of a full grown fœtus, we shall be able to form a very just estimate of the value of an anatomical investigation, in discovering the term of its intra-uterine or fœtal life. But, by the inspection of the thoracic organs, we endeavour to derive an inference still more important; the state of the lungs is supposed to be capable of indicating whether respiration have ever been performed; and, consequently, whether the child was born alive. It is affirmed that the lungs of the fœtus are small, not filling the cavities of the chest, or covering the pericardium; dense; compact; of a deep-red, or chocolate colour, not unlike that of the liver; carrying but little blood, and having a specific gravity exceeding that of fresh water, and, consequently, _sinking_ in that fluid. Upon cutting into them no air will be emitted, nor will any blood follow the incision. When, however, respiration has been established, these organs become more voluminous, present a yielding elastic texture, and assume a florid-red colour; they, moreover, contain and transmit a larger quantity of blood, and have a specific gravity less than that of fresh water, and accordingly _float_ in it. On cutting into the lungs, under these circumstances, the air contained in their cells will escape, and produce a peculiar crackling noise, which has been well expressed by the term _crepitating_; a bloody fluid will at the same time exude.