Page:Thruston speech upon the progress of medicine 1869.djvu/11

9 Here then is a wide field of research opened up by chemists; but very recently other important discoveries have been made in physiological chemistry proper. Foremost amongst them are the labours of Alexander Schmidt and Professor Brücke, on the substances (fibrino-plastic and fibrino-genic) which bring about the clotting of blood, the observations of PettenkofFer and Voit, on the absorption of oxygen and the expiration of carbonic acid gas, at different periods of the day; and the exhaustive researches of Dr Schunck and Dr Thudichum on the chemistry of the urine. Within the last few years also the field of experimental operations has been greatly enlarged, by the introduction of new instruments and methods of enquiry.

By the aid of the telescope, astronomers have resolved the gyrations of nebulae, and have brought the moon within a few miles of the earth; with the microscope, anatomists have unravelled all the most delicate textures of the body; and now, by means of tests of marvellous delicacy, chemists daily perform equal, if not greater, wonders. First amongst these arms of precision must rank the spectroscope, and the Nessler test for ammonia.

The spectroscope will give evidence of the presence of the 180,000,000th part of a grain of sodium, the 72,000,000th of a grain of lithium. The Nessler test will show 1 part of ammonia in 20,000,000 parts of water.

By means of an ingenious adaptation of this latter test, Messrs Wanklyn and Chapman have shown how to determine with facility, the quantity of albuminous (organic) matter in potable water; and by the same method they can discover minute quantities of albumen set free by