On the Latent Period of Muscle Contraction, 



477 



degree of cold after 9° and 10° are reached, produces a more con- 

 siderable elongation of latency. 



If we carry the heating much above this point, we find that there is 

 a sudden accession of excitability of the nerve as manifested by a 

 much elevated and prolonged curve differing also in contour from its 

 predecessors. This condition increases to a certain point, then 

 diminishes, and the entire death of the nerve ensues. The first indica- 

 tion of danger occurs at about 27°, and death at 30°— 31°. This 

 muscle, however, may still be quite capable of responding to direct 

 stimulation if the temperature be not further increased, and revives 

 eventually. The following Table VII shows this course of events. 



Table VII. — Heating carried to Death of Nerve with Measurement of 

 Carves of Direct Stimulation subsequently taken. 



No. 



Weight. 



Temp. 



Length, of 

 latency. 



Length 

 of curve. 



Altitude. 



Remarks. 



1 



10 grms. 



17° C. 



3-10 d.v. 



17-8 d. v. 



24-5 



mm. 





2 



18 



55 



2 -95 „ 



16-7 





25 -0 



33 





3 



35 



19 



53 



2 -75 „ 



16-1 



53 



26 -0 







4 



55 



20 



55 



2 55 „ 



15 -8 



35 



32-5 







5 



53 



21 



55 



2 -45 „ 



16-1 



53 



33-0 



33 





6 





22 



JJ 



2 2 „ 



16 -2 



53 



34-5 



33 





7 





23 



55 



2-15 „ 



15-8 



35 



35'5 



33 





8 



35 



24 



33 



2 15 „ 



15 -8 



35 



36 '5 







9 





25 



53 



2 -15 „ 



15-8 





35-5 



3) 





10 





26 



35 



2 1 „ 



15 



5) 



31 -5 







11 





27 





2-0 „ 



17 -4 



>3 



42 -0 



33 



Nerve irritable. 



12 





28 



33 



2 -0 „ 



18 -9 



55 



54 -0 



35 





13 





29 



35 



9 -05 „ 



19-0 



55 



56 -0 



55 





14 





30 



55 



2-15 „ 



18 5 





55-0 



53 





15 





31 



55 



2-2 „ 



19 -0 





50-5 



35 





16 





32 



55 



o-o „ 



o-o 



33 



o-o 



55 



Nerve dead.j 



17 





33 



JJ 



1 -5 „ 



24-5 



35 



31-5 





18 





32 



35 



1-6 „ 



17 -4 



55 



235 



55 



Stimulation of 



















muscle 



19 



55 



31 



55 



1 -65 „ 



13 -0 



55 



20-0 



33 





N.B. — The muscle completely recovered. A series of curves (direct stimulation) 

 was subsequently taken from it. 



Heating from 17°, at which the latency is 3'10 to 27°, reduces the 

 latency to 2 D.V., and after this point there is again a slight increase 

 till the death of the nerve at 31° occurs. That there is, however, a 

 marked diminution of the latency from 20° to 27°, is plainly to be 

 seen, as the variation is through '003", and this result scarcely coincides 

 with the assumption that conductivity is impaired after 20° in the case 

 of the frog. 



The curarised muscle is a more fitting subject for the study of the 



2 m 2 



