Atlas of photographs of sections of the frozen cranium and brain of the cat (Felis domestica) / by R. H. Clarke and E. E. Henderson.

  • Clarke, Robert Henry, 1850-1926
Date:
[1911]
Catalogue details

Licence: In copyright

Credit: Atlas of photographs of sections of the frozen cranium and brain of the cat (Felis domestica) / by R. H. Clarke and E. E. Henderson. Source: Wellcome Collection.

Provider: This material has been provided by UCL Library Services. The original may be consulted at UCL (University College London)

    2/68 page 392
    und Neurologic. change which in some way alters their characters. Such a change is effected by the degeneration which follows injury and it is difficult to imagine any other agent which would act in such a selective way. By Marchi's well known method this prin- ciple has been applied to the investigation of superficial structures, where small lesions can be produced without injury to adjacent nervous tissues, so that the degeneration is limited to the selected areas and the tracts connected with them. But it is impossible to apply Marchi's method by ordinary operative procedures to deep regions, as the injury inevitably inflicted in exploring them occasions such wide-spread degeneration as to deprive the results of all value for the purpose in view; and so, while this method and electrical stimulation have been extensively applied to the surface of the brain and much has been learned of its structure, ele- mentary functions, and the course of the tracts connected with it, it has been im- possible to carry these investigations into regions where, after all, the most impor- tant centres and tracts are situated, and our knowledge of the latter is very imper- fect. The difficulty can be overcome by the use of needles made of platino-iridium insulated to within a short distance of the points in capillary glass tubes. The needles can be introduced into the brain with very trifling injury, and can be directed to any point by the stereotaxic instrument. By attaching the proximal end of the needle to a battery, with or without an induction coil, electrolytic lesions, from the size of a pin's head to that of a pea, can be produced; or by the use of the faradic current the responses to electric stimuli can be ascertained, and both methods can be employed at the same point without moving the needle. The accidental injury caused by the passage of the needle and the resulting degeneration are slight and generally negligeable and the method therefore fulfils what is requisite for working out the anatomy of the tracts and centres of the brain in a satisfactory way. Physiology. On the physiological side all methods of artificial excitation of the brain are still crude, but with the rapid progress of electrical science it cannot be long before they are improved. They are at present the best means available for testing the elements of localised function, they have given information of great value, and with proper precautions will continue to do so, and with the insulated needle they can be applied with precision to any desired point in the brain. Finally, whatever can be learned from clinical symptoms produced by injury of the brain is valuable in proportion to the accurate localisation and limitation of the lesion which.gives rise to them, and for this purpose artificial lesions made by this method are very suitable. These considerations show that the use of the insulated needle for the purposes indicated is of sufficient importance to the neurologist to enlist his interest in the method of its application which we shall now describe. To direct a needle accurately to any point within the cranium, three requi- sites are indispensable and these are: 1. A system of intracranial topography which enables every cubic millimetre, or similar small area, of the brain to be readily identified, recorded, and referred to. 2. A stereotaxic instrument by which the needle can be mechanically directed out of sight, to any desired point in the brain. 3. A complete series of sections of the frozen cranium and brain, if possible in three planes, or photographs of them, prepared in accordance with the topographical method, to serve as charts or maps, to direct the instrument.
    digitised image 1
    digitised image 2
    digitised image 3