39 



Seluvann, appear pellucid and homogeneous, and of a fluid con- 

 sistence ; but a kind of coagulation soon takes place in that me- 

 dulla, making it easily distinguishable from the tube itself, solid, 

 grumous and much less transparent. Water has the power of 

 producing very quickly that kind of coagulation of the white 

 substance of Schwann, and the more quickly the warmer it is. 



It was interesting to ascertain whether a nerve-fibre keeps or 

 loses its vital properties when its contents have been transformed 

 by coagulation. I have performed two series of experiments in 

 order to solve this question ; one on the motor nerves, the other 

 on the nerves of sensibility. 



1st. After having amputated the two limbs of a frog, I laid 

 bare a long portion of the sciatic nerve in both. Half an hour 

 afterwards these two nerves were still able to act perfectly 

 well. Then a microscopical examination of some fibres from 

 one of these nerves demonstrated that the coagulation of the 

 medulla had begun, but was not yet complete. Ten minutes 

 later the nerves were still capable of acting, and the microscope 

 showed that the coagulation was complete. A similar experi- 

 ment repeated a great many times has always furnished the 

 same result. 



2d. After having divided the two sciatic nerves, not far from 

 the knee-joint, in a living frog, I have dipped the central part 

 of these nerves into water. After a few minutes, some fibres 

 taken from one of them were beginning to coagulate ; yet these 

 nerves possessed their sensibility. Ten minutes after, there was a 

 complete coagulation of the medulla, while the sensibility was 

 very little if at all diminished. 



I draw from these facts the conclusion that nerve-fibres are 

 capable of acting nearly as well when their contents are coagu- 

 lated, as when they are still liquid. 



This result appears to be important, inasmuch as it contri- 

 butes to show that the white substance of Schwann has not a great 

 part in nervous action. Three reasons concur in demonstrating 

 that the essential part, the truly active one that which pos- 

 sesses the vital properties is not the white substance of 

 Schwann : 



1. We see that the vital properties of the nerve-fibres do not 



