42 



Mr. W. A. Jolly. Reflex Times in the 



and 92'5 a. Waller (5) records delays for the crossed reflex in Rana as long 

 as 228 <T. 



The absence of prolonged periods of delay in the spinal frog, and their 

 presence in the decerebrate and intact animals, suggest that in these cases 



the simple spinal reflex has failed, 



Fig. 5. 



Homonymous • 



A: 



27 

 26 

 25 

 24 

 23 

 22 

 21 

 20 



19 

 18 



XI 



16 



L5 

 14 

 13 



1? 

 IJ 

 10 



9 



"B 



"Heteronymous 



Fig. 5. — Diagram giving the reflex times 

 obtained from the hind-limb of the decere- 

 brate frog on homonymous and heterony- 

 mous stimulation of the toes. The times 

 are plotted in thousandths of a second (cr). 

 The diagram shows two groups of reflex 

 times, a group, A, of homonymous reflexes 

 averaging 9o- and a group, B, of heterony- 

 mous reflexes averaging 16'4o-. 



and that we are dealing with re- 

 sponses which involve the lower 

 part of the encephalon. In favour 

 of this view is the fact that in some 

 records we find, in addition to the 

 deflection which obviously represents 

 the spinal crossed reflex, a second 

 deflection, appearing much later in 

 the curve, which seems to be due to 

 a second outflow of impulses from 

 the centres. Thus, in frog E, fifty- 

 two days after decerebration, we 

 have at 23° a deflection occurring 

 15"8(7 after stimulation, and a second 

 44 cr after stimulation, and in the 

 same frog, eighty days after opera- 

 tion at 21-5°, a deflection at 15"3 a 

 and a later one at 41"2 <t. If this 

 view is correct, then these delayed 

 responses should be placed in a class 

 by themselves, and not averaged 

 along with the other responses. 



The following are the average 

 times in thousandths of a second of 

 the heteronymous reflex which have 

 been obtained from decerebrate frogs 

 by the use of the nocuous stimulus 

 at an average room temperature of 

 21-6° C: frog A, 19-4 a ; frog B, 

 15-5 <7 ; frog C, 22 o- ; frog D, 16-8 a- ; 

 frog E, 17-1 0-; frog F, 16-2 o-; and 



frog Gr, 17 0-. The individual times 

 are arranged in diagram (fig. 5) in order of magnitude. 



The average of all these crossed reflex times — thirty-five in number — is 

 18-5 0-. Two of them, both recorded from frog E, are exceptional. In the 



