THE CHEMICAL MAN HELLMUT
BAUER.HIRAM COLLEGE. HIRAM. OHIO
I t has been the custom in the past years at Hiram College to stage an annual scientific exhibit, in which working models illustrating various industries and representing the demonstrational proof of scientific principles are shown. In the department of chemistry a classmate, Vernon Webster, and I had occasion to present an exhibit on chemistry in medicine. Since we wished to depart from the usual nature of an exhibit on this subject, which consists of a host of bottled medicines and numerous posters, we made an attempt to show the chemistry involved in the main functions of the human body. The resulting model was dubbed the "chemical man" of the exhibit. (See illustration on page 2711.) Owing to the technical difficulties and our limited knowledge of the chemistry of the human body, we confined ourselves to four systems: the circulatory, respiratory, digestive, and nervous systems. Consequently, our "chemical man" could eat and breathe; had a heart that would beat; and was sensitive to touch and to sound. The circulatory system consisted of a heart which was operated by an atomizer bulb; and the blood stream passed from the auricles to the ventricles, making a circuit to the principal organs incorporated in the model. To avoid a backward flow of the blood with contraction of the heart, valves were inserted into the arteries of the blood stream. The blood itself was nothing more than a solution of ferric thiocyanate, made by adding ferric chloride to a solution of ammonium thiocyanate. The deep red color of the resulting solution proved to be a very satis$actory imitation of that of blood. In the respiratory system the absorption of oxygen and elimination of carbon dioxide, which is produced by the burning of the tissues in the human body, were demonstrated. Air was drawn in by means of a suction pump attached to one tube through which the used air was drawn out. In a wide piece of hard glass tubing, finely divided carbon was burned to represent the oxidation of the carbon in the human tissues. The resulting carbon dioxide was passed through a solution of clear lime water, which was turned milky by the calcium carbonate formed. The brain of the chemical man consisted of a sound box made by taking the bottom out of a cigar box and stretching a piece of paper over this opening. In the center of this paper was inserted an electric wire, and close to the wire the other end of the circuit comprising the sound system was secured; this was adjusted so finely that sound vibrations closed the circuit and caused the light of a lamp, which was connected to the circuit, to fluctuate with the intensity of the sound waves. The touch system was nothing more than a circuit which was closed a t a certain point by grasping the "arm" of the model. The greatest difficultieswere encountered in the digestive system, where the chemical action involved was much more complex and not nearly so apparent. To show that certain changes occur, we made tests upon the 2710
VOL.7, NO.11
THE CHEMICAL MAN
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food after some time of "digestion." The gastric juice contained highly diluted muriatic acid, pepsin, and rennet, and the food consisted of bread, milk, and eggs. A Fehling's test for sugar was made to show that the muriatic acid had hydrolyzed the starch to sugar; the souring of milk was physically apparent, but nevertheless a test for lactic acid was made by the action of ether on the substance to be tested, subsequent separation in a separatory fume1 and the addition of ferric chloride to obtain a greenish yellow solution. A test for peptones by the action of pepsin was impossible because of the length and tediousness of the procedure.
