VERMINOUS DISEASES. 259 



not being able to support themselves long, they arc 

 soon expelled with the feces. From this observa- 

 tion Dr. Block concludes that it is certainly proba- 

 ble that the filings of tin act on worms by reason of 

 the sharpness and asperity of their particles : and 

 it has been remarked, in fact, that the coarsely 

 filed tin is more efficacious than that which is very 

 fine, because the particles of the former are better 

 suited to irritate the taeniae, and consequently to 

 expel them from the intestines. 



§ C LVII. The tin of Malacca, or very pure tin, 

 called in England grain-tinf{i9il) is preferable to 

 any other, because it is more free from heteroge- 

 neous poisonous particles, which are usually com- 

 bined with this metal.(193) Margraff however 

 prudently admonishes us, that sometimes even in 

 the tin of Malacca and England, we meet with a 

 small quantity of arsenic, which may produce fatal 

 accidents. (194) 



Unfortunately, the tin sold with us, is more or 

 less blended with lead, and the latter is very fre- 

 quently combined with arsenical pyrites ; physi- 

 cians should be very careful of its quality, when 

 they employ tin internally, for I can assert from my 

 own experience, that if the tin be not pure, the sa- 

 turnine or lead colic, and palsy of the inferior ex- 

 tremeties, will be the deplorable consequences of 

 its exhibition. (195). 



§ CLVIII. Tin, coarsely rasped, is, as we have 

 said,(196) to be preferred to tin in fine grains, as 

 used by the English, according to the observations 



