A text-book of physiology . of the wires, amoveable bridge of good conducting material such as brass, which canbe put down to close the circuit or raised up to open the circuit; or in 62 INDUCTION COIL. [Book i. other ways. Such a means of closing and opening a circuit and so ofmaking or breaking a current is called a hey. ? A key which is frequently used by physiologists goes by the name ofdu Bois-Eeymonds key; though undesirable in many respects it hasthe advantage that it can be used in two different ways. It may bea,rranged as in A, Fig. 3. In this case, when the brass bridge of K,the key
A text-book of physiology . of the wires, amoveable bridge of good conducting material such as brass, which canbe put down to close the circuit or raised up to open the circuit; or in 62 INDUCTION COIL. [Book i. other ways. Such a means of closing and opening a circuit and so ofmaking or breaking a current is called a hey. ? A key which is frequently used by physiologists goes by the name ofdu Bois-Eeymonds key; though undesirable in many respects it hasthe advantage that it can be used in two different ways. It may bea,rranged as in A, Fig. 3. In this case, when the brass bridge of K,the key is put down (dotted outline in the figure), so as to form ameans of good conduction between the brass plates to which the wires?are screwed, the circuit is closed and the current passes from the posi-tive pole (end of the negative — copper— element) to the positive electrodeor anode, An. through the nerve, to the negative electrode or kathodeXat. and thence back to the negative pole (end of the positive — zinc —. IFiu. 3. Diagram of Dd Bois-Eeymond Key used, A, for Making and Breaking,B, FOR Short Circuiting. element) in the battery ; on raising the brass bridge (continuous outlinein the figure) the circuit is opened, the current broken, and no currentpasses through the electrodes. Or it may be arranged as in B. Inthis case if the brass bridge be down, the resistance offered by it is sosmall compared with the resistance offered by the nerve between theelectrodes, that the whole current from the battery passes through thebridge, back to the battery, and none, or only an infinitesimal portion,passes into the nerve. When on the other hand the bridge is raised,and so the conduction between the two sides suspended, the current isnot able to pass directly from one side to the other, but can and doespass along the wire through the nerve back to the battery. Hence inarrangement A, putting down the key as it is called makes a currentin the nerve, and raising or opening the key b
Size: 1636px × 1526px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookautho, bookcentury1800, bookdecade1890, booksubjectphysiology
