122 VIS NERVOSA OF ONE KIND. 



fact that the conducting power of the nerves is im- 

 paired or destroyed by injuries to their integrity of 

 every kind ; such as cutting, even though the cut ends 

 are at once replaced in contact, bruising, tying, burning, 

 cauterizing, or chemical alteration, all which impair 

 or destroy vital action, even though they would little, 

 or at all, interfere with electric conductivity. 



Whatever the exact nature of the vis nervosa may 

 be, Beale thinks "it is at least not improbable that 

 the varying effects noticed in connection with the 

 nervous system may be determined by alterations in 

 the intensity of the current and in the conducting 

 properties of the fibres, instead of being due to the 

 transmission of different Idnds of nerve force" 



This is in harmony with the general opinion of physiologists. 

 The motor and sensitive nerve fibres are similar in their funda- 

 mental physiological properties, and both are said to be equally 

 capable of conducting the afferent or efferent nerve current, 

 as was inferred by Lewes, and afterwards supported by the 

 experiments of Kiihne, Phillipeaux, Vulpian, and Kosenthal. 

 Quite recently, however, Vulpian has repeated his experiment 

 of soldering the lingual and hypoglossal nerves ; and he now 

 attributes the motor phenomena to conduction through the 

 chorda tympani, and not through the lingual (sensory) nerve. 

 Both motor and sensitive nerves are likewise equally capable 

 of transmitting the electric current in both directions, and 

 both display the negative variation under excitement. 



We must, however, remember that the specific irritability of 

 nerves differs towards poisons ; the woorari, for example, acting 

 only on the motor nerves, so we must infer specific differences 

 of vital properties in different nerves although the nerve 

 force may be of one kind. 



The nerves of special sense were thought to convey directly 

 an impression of the qualities of outward things to the sen- 



