252 THYSIOLOGY OF MUSCLES AND NERVES. 



and, above all, to the influence of the active nerve. 

 The latter may perhaps, as we have explained in the 

 foregoing paragraphs, be referred back to electric irri- 

 tation. It is thus apparent that muscle and nerve 

 behave essentially in the same way towards irritants. 

 But, remembering that nerves run for part of their 

 course within the muscle, between its fibres, and even 

 penetrate within the very muscle-fibres, the thought 

 now suggests itself, that perhaps the muscle is in no 

 way electrically, chemically, thermically, or mechani- 

 cally irritable ; perhaps, when these irritants are allowed 

 to act on the muscle, it is only the intra-muscular nerves 

 which are irritated, and Avhich then in turn act on the 

 muscle-fibres. In other words, we have to determine 

 whether the muscle is only irritable mediately through 

 the nerves, or whether it is also immediately irritable, 

 independently of the nerves, by any irritants. 



The question is not a new one. Albert von Haller, 

 poet and physiologist (1708-77), asked it, and even he 

 was not the first to do so. Haller declared himself in 

 favour of the second of the two above-mentioned possi- 

 bilities. He called this capacity of the muscles to re- 

 ceive independent irritation (Irritabilitat), and the name 

 has been retained. Haller met with much opposition 

 from his contemporaries ; and a dispute arose which has 

 lasted to the present time. In Haller's days, of courscj 

 only the larger nerve-branchings were known. The 

 further the nerv^es can be traced by means of the micro- 

 scope, the harder does it evidently become to determine 

 the question under discussion. 



6. In the year 1856, the French physiologist Claude 

 Bernard made experiments with a poison brought from 

 Guiana, whicli the Indians of that region use to poison 



