1903.] in the Nerves of Warm-blooded Animals. 277 



rigor at 45 — 50'C,* and the nerves die at 48 — 49°. The proteids of 

 the cat's brain coagulate at 47° C.f Xo data for the bird are available,; 

 the nerves die at 53°. 



In table form. 





Frog. 



Mammal. 



Bird. 



Muscle proteid (Halliburton and von Fiirth) 



40° 



47° 







38—40° 



45—48° 



- 







47° 







40° 











40—42° 



48—49° 



53° 



It is reasonable to conclude from these figures that the extinction 

 of the irritability of the nerve is due to the coagulation of the proteids 

 which enter into its composition, and I venture to forecast, that when 

 the proteids of the frog's nervous system are examined one will be 

 found to coagulate at 40°, and that the two proteids coagulating at 

 40° and 47° are absent from the nerves of the bird. It is possible, 

 therefore, to make a nearer approach to the analysis of actually living 

 nerve substance than has been practicable hitherto. 



Temperature of Extinction by Cold. 



Method. — Alongside the nerve in the nerve-chamber, was placed a 

 junction (A) of konstantan and iron wire, and the nerve was 

 arranged so as to touch this. The junctions konstantan copper (B) 

 and iron-copper (C) were placed in glass tubes and immersed in water 

 at room-temperature, the two copper terminals led to a key-board, 

 with connections to a sensitive Kelvin-type galvanometer of low 

 resistance (16 ohms), and a compensating circuit arranged as shown. 

 The wire rheochord marked 1 ohm was of the ordinary du Bois- 

 Keymond type, and with the voltage and added resistance as marked 

 1° difference between the junction A, and B C, was represented by 

 about thirty-five scale divisions. The compensating current was 

 furnished from an accumulator of large capacity. It was found after 

 careful tests that no perceptible alteration (within 0'05°) of the 



* Yincent and Lewis, ' J. Physiol.,' vol. 36, p. 445 ; see also Brodie and 

 Kichardson, ' J. Physiol.,' vol. 21^ 1897, p. 333, and ' Phil. Trans.,' B, vol. 191, 

 1899, p. 127 ; and also Yernon, ' J. Physiol.,' vol. 24, p. 239. 



t Halliburton, loc. cU. ; also Halliburton and Mott, ' Archives of Xeurology," 

 vol. 2. 



X Deruant, ' Zeitschr. f . Physiol. Chemie,' vol. 3, p. 241, and Kiihne and 

 Chittenden, 'Zeitschr. f. Biol.,' N. F., vol. 7, p. 358, 1889, have made some observa- 

 tions on this point, but I have been unable to consult the papers. 



