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cosm of the human body. And it has here done service, which in practical importance to mankind may perhaps rank with any of its astronomical triumphs. In the first place, the Lucasian Professor of Cambridge, Mr Stokes^[1] has applied the instrument to the detection of the two forms of the colouring matter of the blood, the purple and the scarlet cruorine, and already his method has been turned to account in medico-legal inquiries, aiding greatly in the search for the blood-stains of murder^[2].

Dr Bence Jones and Dr Dupré have, by means of the spectroscope, determined the rapidity of the circulation of the blood, of the absorption of salts by different tissues of the body, and the extent and duration of their sojourn in the organism, and from these experiments they draw the important conclusion, that medicines when taken into the system pass rapidly into every texture of the body, taking with them whatever energy they may possess. It is however only possible for them to act in those parts in which they can share in the processes there going forward^[3].

Dr Bence Jones has also shown^[4] by means of the spectroscope that a fluorescent substance, quinoidine, exactly like quinine in most of its properties, exists in varying amount in most animal textures, and Dr Thudichum has recently communicated to the medical officer of the Privy Council still more surprising results, obtained with this

1. Proc. Roy. Soc. xiii. 335.
2. Sorby, Letheby, Hoppe Seyler, and E. Ray Lankester.
   Dr Bird Herapath was the first to employ the micro-spectroscope in a medico legal inquiry. The case was that of Robert Coe, who was tried for the murder of John Davies at Aberdare. The stains were found on the handle of a hatchet, under the iron ring.
3. Let me illustrate this for a moment by supposing a shower or sheet of alcohol to fall in every part of a room, in many places it would apparently not be present, no action would occur, where there was varnish it would act chemically on the resin, where fire was burning it would burn; and in our eyes it would act chemically, increasing the action there.—Croonian Lectures on Matter and Force, p. 89.
4. Lectures on the Application of Chemistry to Pathology and Therapeutics.