360 PHILOSOPHICAL TRANSACTIONS. [aNNO I766. 



men (presented to the r. s. by me, and now lodged in their Museum) he men- 

 tioned as a proof of its being native tin, that between the ore and the tin there 

 was a mixture of quartz : but, on a nearer examination and some trials with 

 aquafortis, he and another person found it was not quartz. At last, on melting 

 a piece, he perceived no small quantity of arsenic to be mixed with it, and there- 

 fore suspected that the white parts which had passed for quartz were nothing but 

 arsenic. Accordingly he scraped off a little of it and put it on a red hot iron, 

 where it immediately caught fire, and evaporated into smoke, leaving behind it 

 the most poisonous stench they ever smelt. This confirmed some, who had 

 hitherto doubted, in the most firm belief that it really was native tin and genuine, 

 it being impossible for tin to be melted and the arsenic left untouched." 



XL. A Supplement to the Account of an Amphibious Bipes ; Art. XXII. By 



John Ellis, Esij. being the Anatomical Description of the said Animal, by 



Mr. John Hunter, F. R. S. p. 307. 



The tongue is broad and has very little motion. It has a bone similar to that 

 in birds, turtles, &c. On the posterior and lateral parts of the mouth, are 3 

 openings on each side ; these are similar to the slits of the gills in fish, but the 

 partitions do not resemble gills on their outer edges, for they have not the comb- 

 like structure. Above,* and close to the extremity of each of these openings 

 externally, so many processes arise, the anterior the smallest, the posterior the 

 largest ; their anterior and inferior edges and extremity are serrated, or formed 

 into fimbriae : these processes fold down and cover the slits externally, and would 

 seem to answer the purposes of the comb-like part of the gill in fish. 



At the root of the tongue, nearly as far back as these openings reach, the 

 trachea begins, much in the same manner as in birds. It passes backwards above 

 the heart, and there divides into two branches, one going to each lobe of the 

 lungs. The lungs are two long bags, one on each side, which being just behind 

 the heart, and pass back through the whole length of the abdomen, nearly as 

 far as the anus. They are largest in the middle, and honey-combed on the in- 

 ternal surface through their whole length. The heart consists of one auricle and 

 one ventricle. What answers to the inferior vena cava, passes forwards above, 

 but in a sulcus of the liver, and opens into a bag similar to the pericartlium; this 

 bag surrounds the heart and aorta, as the pericardium does in other animals; 

 from this there is an opening into a vein which lies above, and on the left of the 

 auricle, which vein seems to receive the blood from the lungs, gills, and head, is 

 analogous to the superior vena cava, and opens into the auricle, which is on the 



• To avoid the confusion in our ideas, which might aiise from the use of the words anterior, pos- 

 terior, upper, lower, &c, in the whole of this description, the nnimal is considered in its natural 

 horizontal position, so that the head is forwards, the back upwards, &c. — Orig. 



