2 
PROFESSORS V. HORSLEY AND E. A. SCHAPER 
usual Wagner hammer, so arranged that, as with the Helmholtz side-wire, the 
primary current is never entirely opened ; this method we have already described 
elsewhere."'^' The strength of the excitation used was always such as to produce no 
more than a slight pricking sensation on the tongue. The removal of the various 
parts of the cerebral cortex has in all our experiments, except the first few, been 
effected by the knife, or by small cutting instruments specially constructed for the 
purpose. We were led to adopt the knife instead of the galvanic cautery (which had 
been used by Professors Ferrier and Yeo) on account of the greater facility with 
which the lesion can be limited exactly in depth and extent without risk of subsequent 
disintegration of the neighbouring parts, while at the same time the bleeding is not 
markedly greater, and is usually readily stayed by gentle pressure. All these 
experiments have been performed with the strictest antiseptic precautions and under 
carbolic spray, and the wound, after being closely stitched, has been dressed with 
antiseptic gauze, and this again overlaid and rendered firmly adherent to the 
surrounding scalp by a layer of thick collodion so as to make it impossible for the 
animals to tear away the dressing ; at the same time, the collodion, shrinking and 
becoming hard in drying, serves temporarily to support the contents of the skull, 
and to prev^ent their protrusion through the aperture made by the trephine or saw. 
The dressing was always removed within a week after the operation, sometimes 
as early as the third day, and it was almost invariably found that the edges of the 
wound in the skin had completely united, and that the animal could safely be left 
without further dressing or attention. Moreover there appears to be no tendency 
under these circumstances for any extension of the lesion to occur by inflammation of 
the surrounding parts of the brain, nor do adhesions form between the surface of the 
brain and the enveloping membrane, except along the edges of the wound. In all the 
cases liere recorded the animals employed have been Monkeys, but we have not 
confined ourselves to one kind alone, having used indiscriminately individuals 
belonging to various species. They have usually been kept alive for some weeks or 
months after the operation, sometimes being submitted to two or more successive 
ablations at variable intervals of time. In those cases in which the animals have died, 
death has very rarely been due to the shock or, severity of the operation, except in 
the case of lesions producing very extensive motor paralysis, but has been the result 
of accidental causes, and especially of a sort of dysenteric diarrhoea to which Monkeys 
appear peculiarly liable. In most instances the animals have been purposely killed 
after having been sufficiently long under observation, and, the condition of the brain 
having been accurately recorded, the whole of the central nervous system has been 
preserved for future investigation. All the operations have been performed under 
anaesthetics, either chloroform or ether being used, almost always supplemented by 
the hypodermic injection of morphia (as much as from half to one grain of the acetate 
* HoRSLEY and Schafer, " Experiments on the Charactei' of the Muscular Contractions which are 
evoked by Excitation of the various Parts of the Motor Tract." ' Journal of Physiology,' vol. 7, p. 96. 
