1 68 PHYSIOLOGICAL PHYSICS. [Chap. xv. 



are of various forms, usually of platinum wire, 

 because, offering great resistance, it quickly becomes 

 red hot. Fig. 83, 5, shows a galvanic cautery. It 

 consists of a handle of ebonite, in which are imbedded 

 two thick copper wires, which have binding screws for 

 the attachment of the battery wires. Connected with 

 these wires, at the point of the instrument, is a piece 

 of platinum wire a, which is bent as shown in the 

 figure, and flattened at the bend. This piece of 

 platinum wire becomes white hot when a sufficiently 

 strong current is passed through it. Usually there is 

 a spring at the side of the handle for breaking or 

 completing the continuity of one of the wires, 

 so that the circuit may be interrupted or com- 

 pleted. Thus the cold point of the instrument 

 may be accurately applied to the part, then the 

 current sent on, and the cauterising action localised. 

 For making larger eschars the terminal piece of 

 platinum wire is finer and wound on a thin porcelain 

 capsule of any desired shape, or a loop of fine wire 

 may take the place of these. With the current inter- 

 rupted the loop is properly adjusted and tightened 

 round a polypus or other tumour to be removed, and, 

 the circuit being formed, the wire becomes red hot ; 

 it can then be made to cut its way through the 

 tumour. The pain of the galvanic cautery is severe 

 at the moment, but afterwards slight, the extremities 

 of the nerves being destroyed. When the proper 

 amount of heat has been employed, and the tumour 

 cut through not too quickly, haemorrhage is prevented, 

 and healing is rapid. 



Electro-magnetism has been employed in ophthalmic 

 surgery for the extraction of pieces of iron or steel 

 from the tissues of the eye. 



A recent use of electricity in medicine is for the 

 purpose of illuminating certain passages and cavities of 

 the body. Thus lamps of the incandescent type may 



