BY DR. BURDON-SANDERSON. 345 



On these facts are based the electrical method of measuring 

 temperature. Instead of the quadrangle, we give to our junc- 

 tions a convenient form for introducing them into the situa- 

 tions at which we desire to make our measurements. Instead 

 of the magnet, we use the instrument known as a multiplier. 

 This consists essentially of a magnet, surrounded by numerous 

 coils of copper wire, in which the current due to difference of 

 temperature between the two junctions flows. We have to de- 

 scribe first the junctions, then the multiplier. As one of the 

 reasons for preferring the electrical to the ordinary method of 

 measurement is that the measuring instrument can be intro- 

 duced with exactitude into spaces which are too small for a 

 thermometer bulb, the form usually given to the junctions is 

 that of a needle. These needles are generally made of iron and 

 German silver, i. e'., each needle consists of two wires of iron 

 and German silver respectively, which are soldered together at 

 and near their points, so that the junction may be completely 

 buried in any tissue into which the needle is thrust. The two 

 needles forming one element are connected together, metal to 

 metal the iron wire forming part of both, while the two Ger- 

 man silver wires communicate each with the two ends of the 

 coil of the multiplier, thus completing the circuit. As the 

 needles require to be handled by the experimenter, it is neces- 

 sary to protect the upper ends by covering them with silk and 

 varnish ; and the two wires must be carefully isolated from 

 each other everywhere excepting at the points where they are 

 soldered together. 



For the purpose of making clear the mode of using the ther- 

 mo-electric needles, let us suppose that it is required to measure 

 the difference of temperature between two symmetrical parts 

 on opposite sides of the body, one of which is inflamed, the 

 other in the normal state. One or any number of thermo-ele- 

 ments may be used, each of which consists of a pair of needles 

 with their wires arranged as above described. If only one ele- 

 ment is employed, or.e of its junctions is placed in each of the 

 tissues of which the temperature is to be investigated ; the iron 

 wire of each needle being in communication with that of the 

 other, and the German silver wires with the ends of the multi- 

 .plier. If several pairs are used, an equal number of needles 

 must be placed in each of the parts to be compared, the ar- 

 rangement of which is as follows : Let us designate the needles 

 on the right side A, B, c, those on the left A', B', and c'. The 

 German silver ends of A and G f being connected with the multi- 

 plier, the iron end of A is connected with that of A', the iron 

 end of B with that of B', and that of c with c', and the German 

 silver end of A' with that of B, and that of B' with that of c. 

 It is scarcely requisite to say that the junctions need not 

 assume the form of needles ; each may consist of two wires of 



