Abstract
In the paper describing his cage for metabolism experiments the writer 1 referred to the advantages of the “sliding shelf” devised as a holder for the urine receiver, and, in that connection, made the following remark: “The shelf also favors the use of electrical apparatus to ring out the time of elimination of urine-fractions, in experiments in which fractions of the urine must be examined separately and immediately after their natural excretion” (page 407). This remark alludes to one of the several additional devices the writer had intended to perfect for use with the cage described.
In order that an annunciater might be of the greatest service in metabolism work in the way already indicated, and also to insure its usefulness for filtration, distillation and other operations in which the weight of a product above a certain maximum amount could be relied upon to close an electrical circuit and announce the delivery of the material, it was necessary that it should be delicately responsive to the weight of several grams and yet be readily adjustable within relatively wide limits in that respect; that it should be light in weight, of small compass but durable, and resistant to derangement from any cause; also that it should hold, without risk of loss or modification of the contents, any suitable vessel placed upon it.
At the writer's request, Mr. Welker, who has exhibited in this laboratory unusual proficiency in handling electrical apparatus, devised an annunciator to meet these requirements and has perfected an apparatus that is eminently satisfactory for all the purposes contemplated.
The annunciator shown to the Society consists of two square boards (4½ × 4½ × 3/8 inch) securely fastened together with a piano hinge on one side, and kept apart, by a spring perpendicularly arranged at the opposite side, in such a way as to permit a definite pressure to force the surface of the boards together.
Get full access to this article
View all access options for this article.