30 Buchanan 



seen from the records to have arrived at the tirst recording spot of the 

 muscle 20-2o-, 20-5cr, 20-7o-, 20-lo-, IDl^, and 24-4o- after the direct effect, in the 

 successive responses to stimuli applied to the sciatic nerve of the same side, 

 of respective strengths 10,000, 5000, 3000, 5000, 3000, 10,000. A record of 

 one of these (the fourth) is reproduced in fig. 13, A (see p. 62). Above 

 (fig. 13, B) may be seen the record of the response of the same muscle 

 obtained later, when the peripheral end of the sciatic nerve was excited 

 after severing it from the cord. All the records taken with the nerve 

 intact very closely resembled one another. 



In the other preparation the reflex responses occurred 15cr, 15"6cr, 15o-, and 

 25cr after the direct response, the strengths of the stimuli being respectively 

 10,000, 3000, 10,000, 10,000 units. The direct and reflex responses very 

 closely resembled one another, and were about equal in strength ; both were 

 weak in the last response, strong in the others. 



V. The Crossed-Reflex Time. 



I have not yet succeeded in getting from a normal cord a true crossed- 

 reflex effect in response to a single induction shock, i.e. a reflex effect in 

 one gastrocnemius^ when the sciatic nerve of the opposite side was 

 stimulated, although I have tried to get it often in well-cooled decerebrate 

 frogs. Even from the one normal cord, which gave strong same-side reflex 

 responses (fig. 3), no crossed-reflex effect, either mechanical or electrical, 

 could be evoked by such stimulus. I have, however, not infrequently 

 obtained, when very strong induction shocks have been used to excite the 

 sciatic nerve (so strong as to be easily felt on the tongue), responses, 

 mechanical and electrical, in the gastrocnemius of the opposite side, which 

 T might have mistaken for reflex responses, had I not already acquired 

 information about these when the nerve of the same side is excited. Had 

 I only been able to record the mechanical response and to observe the 

 electrical one, it would have been very difficult to know whether they were 

 or were not reflex. The developed photographs, however, showed that the 

 record of the electrical response in these cases was almost precisely identical 

 with the direct efl'ect obtained in response to stimulation of the same-side 

 sciatic, and that it occurred but 1 to I'So- later than this direct response, 

 and consequently long before any reflex response to excitation of the nerve 



' Nor in the seiuitendinosus, nor the biceps femoris (see, however, footnote to p. 59), 

 both of which muscles I have now used a good deal for my experiments (in the summer 

 and autumn of 1907), Professor Sherrington having pointed out to me that muscles 

 which are wholly flexor would be more likely to respond to reflex excitation than the 

 gastrocnemius. The records of electrical responses taken with these two muscles afford 

 confirmatory evidence of all the conclusions come to from experiments made with the 

 gastrocnemius mentioned in this paper. As one would expect, they show that the 

 response is purely reflex (and not preceded by any direct effect) when the sciatic nerve of 

 the same side as the recording thigh muscle is excited near the knee, although it some- 

 times happens that the conditions become, or can be made, favourable for the appearance 

 in the electrical response of the counterpart of what in a mechanical response is known 

 as " paradoxical contraction," and this then precedes the true reflex effect. 



