On the Latent Period of Muscle Contraction, 



479 



appeared to us so far impossible to establish a constant and definite 

 relationship between them for all temperatures and conditions. 



Another result otained from the curarised muscle by heating to 30° 

 after having cooled to 11°, shows the companionship of latency and 

 curve in their variations. 



Table IX. — Curarised Gastrocnemius exposed to Heat and Cold. 



No. 



Weight. 



Temperature. 



Latency. 



Length. 



Altitude. 



1 



10 grins. 



11° 



C. 



3 -5 d. v. 



30 -0 d.v. 



18 *5 mm. 



2 





12 



5' 



3 3 



30-0 „ 



18-5 „ 



3 



jj 



13 



55 



3-0 



24-4 ,. 



18-5 „ 



4 



55 



14 



55 



2 -75 „ 



23 -0 „ 



16-5 „ 



5 



55 



15 



55 



2 5 



20 "0 „ 



17 "0 „ 



6 



55 



16 



55 



2-5 



17-6 „ 



18-5 „ 



7 





17 



55 



2 5 



17-4 „ 



19 -0 „ 



8 



55 



18 



55 



2 -45 „ 



16-9 „ 



19-0 „ 



9 





19 



55 



2-4 „ 



16-0 „ 



18-5 „ 



10 



55 



20 



55 



2 -4 



14-9 „ 



17 -5 „ 



11 



55 

 55 



21 



55 



2-35 „ 



15-2 „ 



17-0 „ 



12 



22 



55 



2-28 „ 



15 2 „ 



16 -0 „ 



13 



55 



23 



55 



2 -25 „ 



14-9 „ 



16-0 „ 



14 





24 



55 



2-15 „ 



14-6 „ 



16-5 „ 



15 



55 



25 



55 



2-12 „ 



14 -4 „ 



18 „ 



16 





26 



55 



2-10 „ 



13-4 „ 



17-5 „ 



17 



55 



27 



2 05 „ 



12. -6 „ 



17 „ 



18 



55 



28 



55 



1-85 „ 



12-8 „ 



17-0 „ 



19 



55 



29 



55 



17 



12-8 „ 



17 5 „ 



20 



55 



30 



55 



1-6 „ 



12-8 „ 



18-5 „ 



The latency varies through 1*9, the curve through 23 2 D.V. The 

 extreme prolongation of the curve at 11° and 12° is an illustration of 

 that which we think we have seen many times, though we have not 

 found opportunity to work out the point, viz., that if after heating 

 a muscle, the temperature be reduced below the normal, the effect of 

 that reduction is greater in prolonging the latency and the curve than 

 it would have been if starting from the normal only. The converse — 

 for heating after cooling — appears also to hold good. 



If a muscle be heated or cooled to a certain temperature and be 

 maintained at that temperature for a considerable time, does the pre- 

 paration acclimatize itself, and do latency and curve show a tendency 

 to return towards the normal ? Oar answer is that they do not. 



A muscle kept at 20° for 25' gave a constant latency of 2*75 D.V., 

 whilst the curve varied in value only through "2 D.V. ; at 25° for 15' 

 the latency remained at 1*65, the length of contraction varying 

 only through '3 D.V., the same result obtained on cooling. 



We conclude then that cold lengthens and heat shortens the latency, 



