CHAPTER IX. 

 MUSCLE. 



IT is impossible to understand the general physiology of muscle and 

 nerve without some acquaintance with electricity. It would be out 

 of place to give even a complete sketch of this preliminary but 

 essential knowledge here ; and the student is expressly warned that in 

 this book the elementary facts and principles of physics are assumed 

 to be part of his mental outfit. But in describing some of the 

 electrical apparatus most commonly used in the study of this portion 

 of our subject, it may be useful to recall the physical facts involved. 

 Batteries. The Daniell cell is perhaps better suited for physio- 

 logical work than any other 

 voltaic element, although for 

 special purposes Bunsen, Grove, 

 Leclanche, and bichromate of 

 potassium batteries may be em- 

 ployed. 



The Daniell is a two-fluid 

 cell. Saturated solution of sul- 

 phate of copper is contained in 

 an outer vessel, and a dilute 

 solution of sulphuric acid in a 

 porous pot standing in the 

 copper sulphate solution. The 

 FIG. 146. DANIELL CELL. latter is kept saturated by a few 



A, outer vessel ; B, copper ; C, porous Crystals of copper Sulphate. A 



pot ; D zinc rod ; D is supposed to be p j ece o f sheet-copper, generally 

 raised a little so as to be seen. f l L 11 



bent so as to form a hollow 



cylinder, dips into the sulphate of copper, and a piece of amalga- 

 mated zinc into the contents of the porous pot. Inside the cell the 

 current (the positive electricity) passes from zinc to copper ; outside, 

 from copper to zinc. The copper is called the positive, the zinc the 

 negative, pole. When the current is passed through a tissue, the 

 electrode by which it enters is termed the anode, and that by which 

 it leaves the tissue the kathode. The anode is, therefore, the elec- 

 trode connected with the copper of the Daniell's cell ; the kathode 

 is connected with the zinc. 



