IN RELATION TO DIET. 605 
residual salt was dissolved in the same quantity of water; proving how there had 
been a loss of the iodine in the operation of boiling; a loss chemists are familiar 
with, of substances in themselves not volatile, carried off suspended in aqueous 
vapour. 
In stating the comparative exemption of fishermen and their families from 
pulmonary consumption, as indicated by the Plymouth Dispensary return, I have 
not given the total number of this class of persons. This deficiency I am now 
able to supply. From information which I have received, for which I am indebted 
to the Registrar-General, it would appear, that of the total male population of 
Plymouth (24,605), the number of fishermen is 726, exclusive of 37 pilots. This 
large proportional number renders the fact of their exemption the more remark- 
able, and especially comparing them with a class of the population, altogether 
different in their habits, and, it may be presumed in their diet, using fish only 
occasionally when abundant and cheap,—these are the cordwainers or shoemakers, 
whose number altogether (males) is 608. Now, on consulting the Dispensary 
return, I find, that the total number of this class that have died of the disease 
under consideration, has been 37, viz., 19 males and 18 females! 
Reflecting on the fact, that iodine has been detected in all the trials I have 
hitherto made on sea-fish, it seemed probable that guano, considering its origin, 
- would not be destitute of this substance; and the result of experiments has been 
confirmatory; using the test-method noticed above. a distinct indication of its 
presence was obtained, both in the instance of the Peruvian and African guano, 
the only two I have yet tried. 
Lusxers How, June 1, 1853. 
