454 NERVE. 



tained. The negative character of the evidence of metabolism is an 

 important circumstance in connection with the rationale of nerve 

 phenomena, and such positive data as exist support the conclusion 

 that nerve metabolism must be very small in amount. 



Waller considers the close agreement between the effect upon the 

 functional changes of external CO.,, and of previous nerve activity, 

 to be an indication that C0 2 is produced during the active state. 1 

 Funke found that nerve fibres had an acid reaction after prolonged 

 activity, such as that caused by strychnia, although alkaline under normal 

 conditions : - the statement has, however, been contradicted by other 

 observers. 3 It is agreed that destruction by heating to 50° C, mechanical 

 pressure, etc., causes the nerve to have this acid reaction. The electrical 

 organ of fish is a nervous structure, being a nerve-ending of a most 

 extensive kind. In the resting state it is faintly alkaline in the 

 uninjured living fish, but after excision it has been observed to be 

 neutral or faintly acid, and it becomes acid when heated to 50° C. 4 By 

 means of intravital injection of acid fuchsine, a dye which is blanched by 

 the normal alkalinity of the tissues, it has been found that the two 

 organs of a strychninised torpedo differ in appearance, if the nerves of 

 one had been divided before the injection. The active-nerved organ 

 was seen to be red, whilst the paralysed one was blanched. 5 This 

 method was found by Dreser to give marked results in muscle : it gave 

 no definite result in nerve. It appears, therefore, that the evidence of 

 acidity during nerve activity is scanty and uncertain. Finally, the 

 blood supply of nerve is too limited to admit of any pronounced meta- 

 bolism, and nerve fibres appear to be incapable of fatigue in consequence 

 of their activity. 



There is the same want of evidence of anv thermal change during 

 nerve activity. Such change was described by Schiff, 6 but the most 

 delicate methods had failed to reveal its development in the hands of 

 other observers." A careful investigation by Eolleston, with the exceed- 

 ingly sensitive method of Callander, confirmed the absence of any 

 appreciable thermal effect. s On the other hand, post mortem changes, 

 such as are produced by chemical reagents or heat, always cause an 

 appreciable development of heat. A development of heat during the 

 activity of the cerebral hemispheres has been observed by Mosso, 9 whose 

 extensive investigations along this line have been taken as proving 

 the localisation of such thermal changes in the central nerve substance. 

 The validity of this conclusion has, however, been disputed ; moreover, 

 the results are opposed by the observation that the production of CO., 

 during cerebral activity is very slightly, if at all, augmented. 10 From 

 these data it is evident that metabolism during activity is either 



1 Waller, " Croonian Lecture," Phil. Trans., London, 1896. 



2 Arch. f. Anal., Physiol, u. v:issensch. Med., 1859, S. 835; Ceatralbl. f. d. med. 

 Wissensch., Berlin, 1869. 



3 Heidenbain, Centralbl. f. d. med. Wissensch., Berlin, 1868. 



4 Boll, Arch. f. Physiol, Leipzig, 1873, S. 99; Weyl, ibid., 1883, Suppl., S. 109 ; 

 Mareuse, " Inaug. Diss.," Breslau, 1891. 



s Rolimann, Arch. f. Physiol., Leipzig, 1893, S. 423. 



6 Arch./, d. ges. Physiol., Bonn, 1871, Bd. iv. S. 230. 



7 Helmboltz, Arch. f. Anat., Physiol, u. wissensch. Med., 1848, S. 158 ; Heidenhain, 

 Stud. d. physiol. List, zu Breslau, 1868, Bd. iv. S. 250. 



8 Journ. Physiol., Cambridge and London, 1890, vol. xi. p. 208. 



9 Mosso, Proc. Pay. Soc. London, 1892, p. 83; "Die Temp, des Gehirns," Leipzig, 

 1894. 



10 Hill and Nabarro, Journ. Physiol., Cambridge and London, 1895, vol. xviii. p. 227. 



