Abstract
Author studied the nerve-endings of the tensor tympani muscles and stapedial muscles of the cat stainning with gold-chloride and Bielschowsky's method.The numbers of the muscles stained by two methods are shown in the following table.
The conclusions of the experimental study were as follows:
1.The motor-endplate :The terminal arborisations of the motor-endplates of these two muscles of the cat were located generally hypolemmally.
Two morphological types of the motor-endplates of the cat's middle ear muscles were identified.One was strongly arborised and sprung from a thick nerve fibre and the other ramified slenderly like a willow-branch and was continuous to a thinner fibre.Between the two types all sorts of intermediate types were observed.
A nerve fibre which entered into a strongly arborised endplate rarely shared a common origin with that which formed a slenderly arborised endplate.
Some muscle fibres received two nerve fibres.Most of these nerve fibres were obviously the collateral to each other, but some of them showed the true double innervation, or″di-segmental″ innervation like the muscles innervated by spinal nerves.
The accessory fibre:In the cat's middle ear muscles there were few accessory fibres.They were found rarer in the tensor tympani muscle than in the stapedial muscle.It was not clear that the accessory fibre is sympathetic or not.
Ultra-terminal fibres were found neither in the tensor tympani muscles nor in the stapedial muscles.
2.The grape-like ending:Up to the time of the present investigations, the grape-like endings in mammals were found in the extrinsic eye muscles, facial muscles and laryngeal muscles, but not in the muscles of body and extrimities except the intrafusal muscle fibres of muscle-spindle.In the cat's middle ear muscles there were a few grape-like endings.This interesting fact is perhaps related to the special function of the muscles for sound transmission and also to anatomical special situation which is innervation by the cranial nerves like above mentioned muscles.
In the cat's middle ear muscles, between the motor-endplate and the grape-like ending there were many intermediate type of nerve endings.
3.The muscle-spindle:In this investigation, the muscle-spindles were divided into two types, i.e.typical and atypical.The latter was composed of only anulo-spiral ending.In 25 tensortympani muscles, only one typical spindle was found, while in the same number of stapedial muscles, a few atypical spindles were found.These observations were also possibly related with their special function.
4.Regarding to the nerve-fibres associated with blood vessels, the branched endings and the bush-like endings in the connective tissue among the muscle fibres, no differences from those of the other striped muscles were recognized.
