Effect of Electrical Stimulation 461 
Experiment 4. In this experiment 20 tadpoles of Rana pipiens 
were selected ranging from 39 to 47 mm. in length. ‘They were 
operated upon December 1, 1908, when 10 mm. of the tail were 
removed. ‘Ten were stimulated December 2, 3, 4, 7, 8, and 10, 
for 5 minutes each day. Current density 1660 0.3 Voltage, 110. 
Four of the stimulated and two of the non-stimulated ones died. 
A comparison of the regeneration of the remaining animals of 
the stimulated set and of the non-stimulated ones shows about 
13 per cent greater amount of growth in the non-stimulated ones. 
The following table shows the amounts of regeneration together 
with the averages for each: 
TABLE II 
Non-stimulated mm, Stimulated mm. 
oD Bag C POR ee AOC SEO eC aera ac yas 10 (aie ec Oty nica Ott een 2.79 
cc Oe AORTIC ERE ES eT Died ML eared mciaests hove aieie See each as 1.62 
BlabAc ISB OL GO DO OIG top TOMeRSe 2.18 Maca cost oApoos ough saNuOOsS a on 2.43 
Tete DO SR IOOLIOE He Lice GO Op RACES Died DAL cia iateye obscene oaxs a's ict chwtte eicie oes 2.25 
Gano S Odo Geto tS STON DOO ere 1.62 Wi Oo sieteeava slotline otetevetana stoves seston erate ale Died 
GR eases ene cine is 2.16 WG: cap tae eas toaster ats aealtre aesy Te7t 
Ce kernicib ton COR eo oO TEE 2.97 Lpinenis Melon ae AT ES ryan 
ORD ci GAGS Ben oe OT en e ene a2 UR ORIHOA A eee ae ApS eet Died 
Cie Gpat Ghadtincae 3 SHA Ooten ae ene 1.98 TQi stereidsstays eee eiaesetaiene stat eletave Cesar Died 
iSagot os dag maCUeouaude’ GaCRSEo 2.43 Po FS eiaPen Si OOOLO 6 DOGO ADCS a Died 
Average AEA cA ORE CO 2354 AVETAREH pianists ea see earache ee 2.08 
Experiment 5. In Experiment five 20 tadpoles of Rana pipiens 
were selected, ranging in length from 48 to 52 mm. They were 
operated upon December 7, 1908, at which time 8 to 12 mm. of 
the tail were removed. ‘Ten of the 20 were stimulated Decem- 
ber 8, 1908, for fifteen minutes. Current density 1660 0. 
Voltage, 110. This was repeated upon the following day. All 
were measured December 15, 1908. ‘The following table shows 
the amount of regeneration for each. The averages give an 
advantage of 44 per cent to the non-stimulated set: 
39 as proposed by Hermann and Matthias, is a unit of current density equal to one-millionth of an 
ampere of current per square millimeter. See C. B. Davenport, Experimental Morphology, part i, 
p- 128. 
