176 Dr. J. S. Lombard. On the Propagation of 



corresponding points of the two hemispheres of large dogs, the perma- 

 nent galvanometric deflections, showing the difference of temperature 

 between the two points, were about 15° of the scale, which was divided 

 into millimetres.* Now it is very unlikely that the temperatures of 

 two points of opposite sides of the brain would, on an average, approxi- 

 mate each other nearer than by o, 03 C, — this after making full 

 allowance for the good conductivity of brain-tissue. In practice it is 

 difficult to find in the different tissues, unless the points examined are 

 within a centimetre of each other, a nearer approach to equality than 

 the difference just given. Of course, still smaller differences may be 

 met with by accident, but one cannot count upon finding them at a 

 venture. The dogs are specified as large, and, indeed, in one place, f 

 M. Schiff gives the distance between the two points examined. In 

 this case each pile was 15 millims. from the longitudinal median line ; 

 the two points examined were consequently at least 30 millims. apart. 

 We may assume then that the 15° of the galvanometer did not repre- 

 sent less than 0°'03 C. ; therefore 1° of the galvanometer was equal to 

 o- 002 C. Now the simple odour of food with these animals caused 

 deflections of 6° or 7°, equal to 0°'012 0. to 0°-014 0.,{ and the masti- 

 cation of food increased these figures to 12° and 14° of the galvano- 

 meter, equal to o, 024 C. and o, 028 C. It must, however, be borne 

 in mind that these deflections did not by any means represent the total 

 rise of temperature, but only the difference of rise between the two points 

 examined. All M. Schiff' s results are in fact relative, based on the 

 assumption that one of the two points examined would rise in tem- 

 perature more than the other. The use of the second pile with him 

 was, in fact, principally for the purpose of keeping the primary deflec- 

 tion of the galvanometer within the field of division on the scale, this 

 pile thus serving as a compensating element. Now if a difference of 

 rise of temperature of from 0°'012 C. to O- 028 C. can be produced in 

 the two hemispheres of the dog by the feeble cerebral action excited by 

 the means given, it is certain that the thermal effects of the active 

 exercise of the intellectual and emotional faculties of man may be 

 estimated in, at least, tenths of a degree Centigrade. 



In the case of the experiments on fowls, we have further and still 

 stronger proof, both that the apparatus was not excessively delicate, 

 and also that the alterations of temperature were not so very small. 

 In these experiments the thermo-electric arrangement was a small bar 

 of bismuth 4 to 5 millims. long, in the two ends of which copper wires 

 were buried to a depth of 1 millim., thus forming a thermo-electric 

 junction at each end. As the copper wires were embedded in the 

 bismuth to a depth of 1 millim., the two junctions were only from 2 to 



* Loc. cit., pp. 205, 207. 

 f Loc. cit., p. 211. 

 % Loc. cit., p. 210. 



