Davis[136] gives a list of twenty-nine patents for bating issued by the U.S.A. Government from 1790 to 1883 inclusive. I do not know whether any of these are in use at the present day.
Erodin.—Since the publication of the authors researches on the constitution and mode of action of the dung bate, renewed attention has been given to the construction of bates, or puers, having an identical action. One of these has been worked out by Professor Dr. H. Becker, of Frankfort o/M, in conjunction with the author under the name of Erodin (Latin, erodere, the equivalent of the German beizen—to bate).
As this was the first artificial bate in which a pure culture of bacteria has been applied to the treatment of skins, I propose to describe it in some detail.
Erodin[137] consists essentially of a nutrient material in the form of powder and of a pure culture of B. erodiens which is added to the powder mixed in a definite quantity of warm water (40° C.). On the average about 10 grm. of this material is sufficient to bate one kilo of wet prepared skin.
In practice it is found that this material acts far more energetically on the skins when living bacteria are present in the liquid; we suppose that they penetrate the skin and form their products in the intercellular spaces. It was found that, in the evaporation of the cultures to dryness, the bacteria were mostly killed or so far reduced in activity, that on preparing the bate after a certain lapse of time it was liable to become infected by foreign organisms.
In order to ensure uniform results a pure culture of the special bating bacteria is supplied with every 5 kilos of the erodin powder. The weighed amount of erodin is placed in a perfectly clean mashing-tub, with 50 times the weight of water at a temperature of 40° C. a pure culture of Bacillus erodiens is added to the mixture, and the whole covered with a clean cover and allowed to stand for two or three days. A little steam is admitted morning and evening so as to maintain the temperature at about 40° C., or some other suitable device for heating is applied. Several tubs may be kept in a small stove heated to the right temperature by steam pipes. In this way the bating bacteria develop rapidly, and if the proper precautions as to cleanliness and temperature have been observed, there is no fear of any adventitious germs getting the upper hand. As soon as a vigorous growth is attained, usually on the third day, the bate is ready for use.
Erodin is in use on a fairly large scale, and, as is usually the case, difficulties have arisen on a manufacturing scale which do not occur in the laboratory. In the practical application of the material the mashing-tub may be 3 ft. 9 in. in diameter and 3 ft. 3 in. in height and of a capacity of 200 galls. Steam is admitted directly by means of a copper pipe fitted with a boiling jet.
The goods are bated in the ordinary bating paddle or puer wheel (Fig. [3], p. 13).
During the year 1901 about 9000 dozens of sheep “grains” were puered with Erodin at Trent Bridge Works (Messrs. Turney Brothers, Ltd.) Nottingham, and considerable experience gained in its use.