The involuntary nervous system / by Walter Holbrook Gaskell.

  • W. H. Gaskell
Date:
1920
Catalogue details

Licence: In copyright

Credit: The involuntary nervous system / by Walter Holbrook Gaskell. Source: Wellcome Collection.

    40/200 page 24
    mass of nervous material, and so enabled a more efficient con¬ centration of the elements of the voluntary nervous system. At the same time the involuntary connector fibres, which form the efferent part of the rami communicantes, were sufficient to maintain the necessary efficiency of the interaction be¬ tween the central nervous system and the motor cells of the involuntary system, taking into consideration the nature of the movements of involuntary muscle. These movements are essentially movements en masse and not delicately co-ordinated movements, such as are so characteristic of the voluntary system ; indeed, the evidence shows that movements of the involuntary system of muscles, brought about reflexly through the central nervous system, always involve a large number of muscle fibres. This must be the case when we consider that each single fibre that leaves the central nervous system can activate by means of collaterals many motor nerve cells, each of which in its turn innervates many muscle fibres. The limits of the outflow of nerves from the spinal cord, which pass to the cells of the sympathetic ganglia (Fig. 4), are defined by the structure of the anterior roots and consequent presence or absence of a white ramus communicans. The upper limit is defined by the brachial plexus and the lower by the lumbo-sacral plexus. The next question for consideration was whether there were similar outflows of fine medullated efferent fibres either below or above these limits. To settle this question I proceeded to cut sections of the anterior roots of all the spinal nerves, and found that again in the anterior roots of the second and third sacral nerves there was evidently another mass of these small medullated fibres. It was easy to follow these small fibres outwards into two separate nerves which joined together to form the nervus erigens ; that is to say, the structure of these roots demonstrates an outflow of fine medullated fibres from the spinal cord, to form a ramus communicans, not to any ganglia of the verte¬ bral chain, but to separate sets of ganglia lying on the surface of the bladder and rectum (Fig. 5, P). These fibres pass directly to these ganglion cells without having anything to do with the lateral or main chain of sympathetic ganglia, just as the nerves, which form the splanchnics, pass direct to the collateral ganglia of the sympathetic independently of the lateral
    digitised image 1
    digitised image 2
    digitised image 3