PRESERVATION OF FISHERY PRODUCTS FOR FOOD. 
509 
An objection to the canning of small flsh is the large number of bones. Ordi- 
narily the heat developed in the process of canning destroys the cohesion of the 
particles of the bones, so that they may be masticated and swallowed without incon- 
venience, but the bones of some small fish are not so easily softened. About 1867 
it was found that by placing the fish in vinegar and subjecting them to a temperature 
of 170° F. for several hours, according to the size of the bones, the acid of the vinegar 
dissolves the lime salts contained in them. This process is somewhat costly and the 
vinegar is objectionable to some consumers. 
In 1872 it was found that the bones could be softened without using vinegar, by 
successive steamings for several hours, with an intervening cooling. A patent for 
this process was issued May 21, 1872, to Isaac L. Stanly, of Hew York City, who thus 
describes the process with special reference to canning menhaden; 
First put the iish, after being dressed and prepared, into open tin or other suitable boxes or 
vessels, and place the same in a steam chest, which is afterwards closed. In this couditioii steam the 
fish with steam of 212° F., or thereabout, for 5 hours, more or less, after which they are taken out of 
the steam chest and put on tables to cool and drain for about 5 or 6 hours. The fish are then packed 
in tin boxes filled with olive or other oil, and the boxes afterwards closed and the covers soldered or 
sealed. Said boxes containing the fish are next put into a tank or chest, which is afterwards closed, 
and heated by steam or otherwise to a temperature of from 217° to 220° F., or thereabout, for a period 
of from 2 to 5 hoursj according to the size of the fish or its bones. 
An objection to the use of tin cans in iireserving food products is the liability of 
the lead in the can to atiect and taint the contents, which sometimes results in lead 
l>oisoniug. This danger is not great when good materials are used in making the 
cans, except when they are filled with such articles as shrimj), the acid in which acts 
upon the tin. This is remedied by introducing a lining between the inner surface of 
the can and its contents. This lining may be textile fabric or a coating of asphaltum 
cement. Silver plating has been employed, and a lining of selected corn husks has 
also been used to a limited extent. For an account of these methods see pp. 523 et seq. 
The most satisfactory way of overcoming this liability to lead poisoning is by 
using cans sealed without the use of solder. There are several varieties of these cans 
on the market at present, the joints being made tight by introducing a gasket or 
washer of rubber, paper or similar material between the overlapping tin and crimping 
or folding the edges so as to hold them together. Some of these cans are drawn by 
machinery out of one solid piece of tin plate, and others have an outside soldered 
seam in the body only. The additional cost of these cans has confined their use to 
the preservation of the more costly varieties of marine iiroducts. 
A great improvement in canning was the introduction, about 25 years ago, of 
the use of solder in the form of twisted strands cut into rings of the jiroper size 
and containing on its surface the proper quantity of flux. By twisting a strand, or 
by uniting two or more strands into a cord, the exterior will contain a multitude of 
small depressions. The wire is converted into rings by winding it on a wooden 
cylinder of the required diameter, a cut is made through the wire the whole length of 
the cylinder, and the rings are slipped off. The rings are coated with resin or other 
suitable flux, the depressions become filled with it and hold a sufficient quantity for 
soldering purposes. This quantity is regulated by the method of twisting the wire 
or the manner of applying the flux. If to be used for square tops, the wire is wound 
on a rectangular block of the required size and then cut. It is apparent that when 
these rings are applied to the capping of tin cans no more solder or resin need be used 
