Extirpation is the localized extinction of a species. This can be due to over-hunting, human development, climate change, or competition from introduced species. It is especially common on islands where only a small and therefore vulnerable, population may exist. Sometimes species are reintroduced to an area from which they were extripated, although this may cause controversy as during the reintroducution of wolves to Yellowstone National Park. In other instances, species return to an area on their own, as their range expands or their population recoves from some pressure, as seen in the return of wolves to the state of Michigan.
Naturally the methods available for the investigation of the cortex at present, by means of extirpation of different parts, can but lead to entangled pathological states, and even the most guarded deductions with regard to the constitution of the cortex cannot therefore be ensured against a high probability of error.
In this manner the endeavour to demonstrate by means of experiments with extirpation the disappearance out of the normal cortical activity of the functions related to the extirpated part is complicated in the first period after operation by the general effect which the operation has upon the hemispheres as a whole.
It is unfortunate that the majority of our experiments with extirpation were performed in the earlier period of our research, when we had not definitely realized the peculiarities of the different individual types of the nervous system and had not yet any knowledge of the pathological effects arising under the influence of functional, i.e.
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