471 



liable to produce this prejudicial effect, 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. 



Additions to an Account of the Anatomy of the Squalus maximus, con- 

 tained in a former Paper ; with Observations on the Structure of the 

 Bronchial Artery, By Sir Everard Home, Bart. F.R.S. Read 

 June 24, 1813. [Phil. Trans. 1813, p. 227.] 



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 different species of Squalus. 



Of the internal parts, the stomach is now described, and a delinea- 

 tion 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 au- 

 thor to be 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 piscatortus, the mechanism of the heart is such, that 

 description alone could hardly convey an adequate idea of its form ; 

 and a drawing of its peculiarities is annexed. 



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 coats of the ventricle. 



