liable to produce this prejudicial efi'ect, although they prevent the
formation of white sand;-—-
And that carbonic acid appears particularly useful in cases where the irritability of the bladder forbids the use of other acid remedies.
The author observes, that with respect to his former description of the external parts, he has no addition to make, excepting that, from the position of the fish at the time when it was drawn, a small fin was omitted between the anus and tail; which, however, is so far important, that some persons have on this ground imagined that the fish described was a difl'erent species of Squnlus.
Of the internal parts, the stomach is now described, and a delineation given. The liver has six ducts; but these unite, before they enter the duodenum, in one common cavity, which corresponds to the dilatation of the common duct in those quadrupeds that have no gall-bladder.
A drawing is given of the heart and valves of the bronchial artery; and it is remarked, that the coats of this artery are muscular to some distance from the ventricle, the use of which is conceived by the author to he to aid in propelling the blood through the gills when impeded by the pressure of any great depth of water: for the same quantity of blood should pass through the gills at all depths, unless the water at greater depths contained a larger proportion of air; but this did not appear to be the case by direct experiment, in which the author was assisted by Mr. Brande.
In support of the opinion that muscularity of the coats of the bronchial artery is connected with the circumstance of living at great depths, the author remarks, that in the turbot and the wolf-fish, which live in shallow water, there is no muscular covering to the origin of the bronchial artery, but, on the contrary, its coats are so exceedingly elastic as to be easily dilated into a considerable reservoir.
In the Lophius piscutorius, the mechanism of the heart is such, that description alone could hardly convey an adequate idea of its form; and a drawing of its pemdiarities is armexed.
In the tribe of Mollusca, other differences of muscularity occur from other causes. In the Teredines, where great muscular power is required for working the boring engine, the heart consists of two auricles and two ventricles, with valves of very great strength, to direct the current of the blood. But in the oyster, on the contrary, the heart has but one auricle and one ventricle; and in the muscle, the heart is scarcely divided into auricle and ventricle, but is a mere oval bag, through which the intestine passes, the peristaltic motion of which appears to the author to contribute as much to the motion of the blood as can be effected by the proper ceats of the ventricle.
