1883.] Variations of Latency in certain Skeletal Muscles. 283 



Toad. 

 Table II. 



The averages of several experiments made during December and 

 January. Fresh specimens which as a rule had been but one night 

 in captivity were examined. (The weather having been very mild 

 during the time of experimentation the animals were active and 

 vigorous.) 



Muscle. 



Weight. 



Length of latency. 



Gastrocnemius . . 



10 grms. 



■0123" 





10 „ 



•0121" 



Hyoglossus . . . . : 



6 „ 



•0191" 





6 „ 



•0191" 





6 „ 



•0135" 





6 „ 



•015" 



March. — From perfectly fresh Toads the following variations in values 

 were obtained. The animals had not spawned : — 



Muscle. 



Yariation of length of latency. 



a' 



Gastrocnemius .... 



•0135" .... 



•0146" 





•0128" .... 



•0128" 



Hyoglossus 



•015" 



•0192" 





•013" 



•015" 





•015" 



•0155" 





•0137" .... 



•0146" 



The durations of the latencies in the latter part of Table II differ 

 but slightly from those obtained from the "winter frog," as will be 

 seen from contrasting the following muscles : — 



Muscle. 

 Gastrocnemius 



Triceps 



Hyoglossus . . . 

 Biceps crur. . . . 

 Rectus abd. . . . 



(Fresh) Toad 

 (March.) 

 •0135" 

 •0128" 

 •015" 

 •015" 

 •013" 



Frog 

 (December). 



•0117" 



•0114" 



•015" 



•0124" 



•014" 



It is worthy of note that the more pronounced differences of latency 

 between toad and frog lie in the muscles of the extremities ; the 

 trunk muscles yield more nearly equal values. An appeal to function 

 shows that the circumstance is highly probable. The frog which 

 depends upon speed of movement for procuring its food, for safety 

 from enemies, and preservation from death in times of drought, has 

 different motor requirements from the toad, which depends for safety 



