471 



far cxs possible from the magnet, in order to diminish its deviating 

 action on the cathode ra3^s ^). In some cases the patient may be 

 treated while standing, which is much simpler. 



Deep-seated intestines f? — 20 cm. under the skin) are treated 

 without pole-shoes. For those lying nearer the skin, the following 

 pole-shoes are used which may be made of a highly satnrated, 

 polished and nickeled, substance, such as ferrocobalt. 



'J. A "drawing-pole" in the form of a truncated cone with a semi- 

 angle of 40° ; the attraction is strongest in the apex of the cone. 

 The contents of the intestines may be first drawn towards a par- 

 ticular spot and then attracted towards the magnet. 



2. A prismatic pole with a semi-angle of 32° for the treatment 

 of longer intestinal sections. 



3. An unsymmetric hoof-shaped "d ragging-pole" for applying foi'ce 

 parallel to the peritoneum. Starting from the above-mentioned principle 

 it may be shown that a maximum gradient of -^"^ is reached when 

 the narrow pole front forms an angle a = 65°54' = tg--^ |/5 with 

 the direction of dragging. For a very long prism on the other hand 

 it ought to be a = 60° = tg~^ ! '3. In this way the best adapted shape 

 of the pole-shoe may be determined, also titting the cylindrie core. 

 For special purposes pole-shoes of vai'ious shapes may be designed. 



The forces used here have often been measured with small iron 

 test-spheres. The force component is 



F, = — t^ÓT^ — -^, 

 4.T Ox 2 dx 



V denoting the volume, r the radius, there being no question of 

 saturation. This expression is quite independent of the nature of the 

 substance if only this is not too weakly ferromagnetic. The force, 

 expressed as a multiple of the weight G of the test-sphere will be 

 greater, the smaller the density of the latter. The value FxlG=^l 

 corresponds to the case that at a certain distance under the magnet 

 the sphere is just being prevented from falling down. Considering 

 this, spheres were made of magnetite {F,0^ =:. ferroferrite = ferr. 

 oxyd. oxydulat. nigrum.) which quite fulfilled my expectations. Best 

 of all proved small spheres of 1 cm. diameter of i^jO^-powder 

 mixed with a little mucilage and some light neutral powder; generally 



1) The RöNTGEN-tube is moved by the foot of the operator. The deviation of 

 the cathode-current is proportional to its own .strength, tiie value of the field at 

 that place and the sine of the angle between these two directions; these three 

 quantities ought to have low values. An iron-clad RöNXCEN-lube might prove useful ; 

 but sparking constitutes rather a dilficulty. In some cases a compensating coil 

 near the cathode rays may be arranged. 



