NERVES OF MUSCLES AND TENDONS. 1009 



bodies of simple type. 1 They are not equally distributed through the muscula- 

 ture. Huber 2 agrees with me in thinking that they are disproportionately 

 frequent in the small distal muscles of the limbs. Kolliker noted fifteen 

 spindles in each belly of the omohyoideus. I failed to find 3 any at all in the 

 following muscles : — Recti and obliqui oculi, levator palpebrce superioris, the 

 intrinsic muscles of the tongue and larynx. Cipollone 4 notes their absence 

 from the muscles of facial expression, although present in the masticatory 

 muscles (pterygoids, masseter). 



Kuhne 5 has insisted on certain resemblances between the muscle spindle 

 and the electric organ, which is stated to be derived from muscular tissue. 

 Kerschner 6 argues the muscle spindle to be an organ in which the " action 

 current " of muscle forms the stimulus to the sensory nerve fibres. 



The Golgi-organ of tendons. — These sensorial end-organs were earliest 

 described by Rollett, 7 but for the first time fully by Golgi, who studied them in 

 mammals, birds, and reptiles. The organ consists of terminal arborisations 

 of one or of two myelinated nerve fibres, the arborisations permeating 

 as a richly branching tree, the thickness of a tendon bundle, which is 

 somewhat sharply marked off from the surrounding tendon bundles. The 

 terminal arborisation is of great size and complexity, and extends hi some 

 cases for 500 fx along the tendon bundle. The organ has often a distinct 

 capsule, and is well supplied with blood vessels. Like the muscle spindles, 

 they seem particularly large and complex in the higher mammals. The tendon 

 bundle in which the Golgi-organ lies can often be traced to receive the 

 insertions of muscle fibres that belong to muscle spindles. The Golgi-organ 

 affects particularly that region of the general tendon which adjoins the flesh of 

 the muscle. These organs are found in the tendons of the eye muscles, which, 

 as I have pointed out, are muscles devoid of spindles ; but the great number of 

 sensory nerve-endings in the eye muscles are smaller and simpler than the 

 ordinary tendon organs. 



Large end-bulbs, or, as they are called by the Italian authorities, "modi- 

 fied Pacinian bodies," are also met in muscle tendons, especially in the sheaths 

 of tendons, and of the muscles. For description of them reference can be made 

 to Ciaccio, 8 Mazzoni, 9 or Ruffini. 10 



Pacinian corpuscles occur in connection with tendons, also in the septa, 

 and in the perimysium internum of muscles, and even embedded in the fleshy 

 tissue. 11 



The individual contributions toward muscular sense of these different sets of 



end-organs can only be conjectured. In the skeletal muscles there are, as we 



have seen, three sets of sensory organs, e.g. muscle spindles, tendon organs, Pacini 



corpuscles modified and typical. The fact that of these, one set, the spindles, 



are contractile, suggests that they function in signalling active movements 



rather than passive. Throughout the body it is remarkable how great a part 



mechanical actions play as stimuli to protoplasm. It has been argued that 



the action current is the immediate physical stimulus for the sensorial endings 



in muscle. That is plausible, although some of the arguments brought 



forward, such as the initiation of the kinsesthetic idea in the latent period of 



the muscular response, are weak. The possibility that the immediate stimulus 



consists of chemical products of the muscle has been discussed by G. E. Miiller 



and Schumann, 12 but remains little more than a suggestion. If suggestion is 



profitable, it seems to me more likely that the immediate stimulus of the 



muscle spindle is of a mechanical kind, produced by the change in form of the 



1 Cattaneo, loc. cit. - Journ. Comp. Neurol., 1898. 



3 Journ. Physiol., Cambridge and London, 1894, vol. xvii. 4 Loc. cit., p. 211. 



5 Virchow's Archiv, Bd. xxx. S. 206. 



6 Bcr. d. naturw. -tried. Ver. in Innsbruck, 1897, Bd. xxiii. 



7 Loc. cit., 1876, in the frog. 8 Loc. cit. 9 Loc. cit. 10 Loc. cit. 



11 Rauher, "Festschr. f. Bischoff," 1883 ; Ruffini, loc. cit. ; Sherrington, loc. cit. 



12 Arch./, d. ges. Physiol, Bonn, 1889, Bd. xlv. S. 37. 



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