376 TENTH ANNUAL REPORT OP 



fhat the increase of specific heat is proportional to the increase of the 

 rise of temperature. Whether this he true or not we shall not 

 attempt to decide ; hut if it were the case, the converse woukl he 

 proved, of what Miiller desires ; for, according to the determinations of 

 Lenz, the increase of resistance to conduction is not proportional to 

 the increase of temperature ; the hypothesis of Miiller would, per- 

 haps, accord better with the measurements of Becquerel. 



Miiller now compared the increase of the specific heat of mercury, 

 platinum, copper, zinc, silver, and i^-on, with the corr; -^ponding in- 

 crease of resistance ; the accordance is no: remarhahle. This, how- 

 ever, in Miiller's opinion, does not militate against his assumption of 

 the dependence of the increase of resistance on the specific heat, 

 because the determinations of specific heat at different temperatures 

 have not been carried to the requisite degree of accuracy. If this 

 want of accuracy be admitted, as in fact it must be, we must also 

 admit that to try to prove such a relation with our present knowedge 

 of facts is, to say the least, a fruitless endeavor. 



§ 31. Bedstance of ilie human body to co.idudion. — Lenz and Ptschel- 

 nikoflf have investigated this subject, and made use of a magneto-elec- 

 trical spiral as an electro-motor. According to their determinations, 

 the resistance of the human body, the whole hand being immersed in 

 water with the addition of j^o part of sulphuric acid, is equal to that 



of 



91762 



metres of copper wire 1 millimetre in diameter. This can be considered 

 'as only a rude approximation, consequently the description of the de- 

 tails of the experiment is not necessary. 



Pouillet previously (P. A. XLII, 305) estimated the resistance of 

 the body at 



49082 



metres of standard wire. 



Although these numbers may be very inaccurate, they nevertheless 

 show us that the resistance of the body is very great, and that, there- 

 fore, the strength of the currents which produce physiological effects 

 is always very feeble. 



Suppose a human body introduced into the closing circuit of a 

 Bunsen's battery of 50 cups, the strength of the current will be 

 50 X 800 _ 40 _ 

 49000 ~ 49 "~ ■ 

 by assuming the electro-motive force of a Bunsen element to he in 

 round numbers z=. 800, and the resistance of the buttery (ahoiit 500) 

 being disregarded when compared with that of the body, provided we 

 take for the resistance of the body the smaller number of Pouillet. 

 This force of current corresponds to a deflection of about f of a degree 

 of our tangent compass. A single Bunsen clement closed by the body 

 would thus give a force of current of only 



