will effect in those cases where the gaseous distention has arisen from respiration. From the view which we have taken of the _hydrostatic_ test, and of the objections which have been urged against its validity, the practitioner will be enabled to appreciate its importance. _Plouquet_, desirous of procuring additional evidence, respecting the existence of respiration, from the condition of the pulmonary organs, proposed a test founded on the _absolute_ weight of the lungs compared with that of the body. Respiration produces two important changes in them—by inflating their texture it _diminishes_ their _specific gravity_; and by promoting a determination of blood to their vessels, it increases their _absolute_ weight; upon the former of these changes, the _hydrostatic test_ is founded, as we have already explained; on the latter, _Professor Plouquet_ endeavoured to found his “_Nova Docimasia Pulmonaris_,” which is now very generally known by the name of _Plouquet’s test_, or _assay_. The blood-vessels, observes this distinguished physiologist, being collapsed and compressed in the lungs of the fœtus, admit only a small portion of blood; but after respiration, being dilated, and extended, and more free in the expanded lungs, they receive a greater quantity; in consequence of which they become still farther expanded, and of greater calibre. As this increased capacity of the vessels is necessarily _permanent_, a greater quantity of blood will remain after death in the arteries and veins, and more especially in the latter, than in the lungs of those infants who have never respired, and consequently the _absolute weight of the lungs must be increased_. In conformity with these views, _Plouquet_ found on examination, that the body of a male infant, born dead, and which had not respired, weighed 53040 grains, the lungs inclusive; and that these latter organs alone weighed 792 grains; the proportion of the lungs to the body, in weight, was therefore in this case as 1 to 67. In another infant, under similar circumstances, he found the proportion as 1 to 70. On examining an infant, born at the full period, and which had respired, the proportion was found to be as 2 to 70, so that the weight of the lungs was absolutely doubled by the act of respiration.