332 



Dr. A. I). Waller and Miss S. 0. M. Sowton. [ June 12 > 



ordinary care, a portion of spinal column being removed with them to 

 serve as handles, and kept until required in physiological saline, which 

 is best made with tap water and must not have the slightest acid 

 reaction. The usual value of the normal response of a satisfactory 

 nerve is between O'OOl and 0*002 volt, and the time during which a 

 nerve may be employed for experiment is usually at the least 24 48 

 hours after excision. Quite fresh nerves may be used, but it is prefer- 

 able to use nerves that have remained in physiological saline for an 

 hour or two after the removal from a freshly pithed frog, and it is 

 unadvisable to make use of nerves that have been left for any con- 

 siderable length of time in the tissues of a pithed frog. 



Fig. 3 (Plate 3492) gives the result of a typical experiment upon a 

 frog's nerve submitted to the influence of a strong solution of betaine 

 hydrochloride (10 per cent, neutralised by half its volume of normal 

 soda solution). 



FIG. 3 (Bcta'ine hydrochloride). 



vA 



A .summary of our observations is given below ; we have included 

 in that summary for the sake of comparison seven observations on a 

 sample of Calmette's snake venom (received from Professor Wright, of 

 Netley), on a sample of tetanus toxine (from Mr. Plimmer, of the 

 Lister Institute), and on some decomposed serum-albumin. 



N.B. Throughout this series of experiments the unit in which the 

 deflection values of the current of injury and the negative variation is 

 expressed = O'OOOl volt. 



