1910.] A fferents of Third, Foui'th, and Sixth Cranial Nerves. 451 



nn. trigemini, combined with severance of both optic nerves, even after 

 transection of the encephalic bulb, does not obviously depress the tonus of 

 the eye-muscles (extrinsic). Since severance of the afferent nerves of 

 muscles does almost universally depress their tonus severely, the inference 

 ■was drawn that in the case of the extrinsic eye-muscles their tonus is not 

 dependent on trigeminus or opticus, and may, therefore, be referable to 

 afferents contained within the third, fourth, and sixth nerve-pairs them- 

 selves. 



To examine further the whole question, the experiments and observations 

 forming the basis of the present communication have since been undertaken. 



A. Characters of Nerve-endings and Nerve-fihres Normally Present in the 

 Extrinsic Eye-rmiscles. — Renewed examination has been made of the intra- 

 muscular nerve-twigs and nerve-endings of the normal eye-muscles of rabbit, 

 cat, and monkey. For this purpose use has been made chiefly of the intra- 

 vitani methylene blue method of Ehrlich and of osmic acid for staining and 

 fixation prior to weak dissociation and teasing. In carrying out the 

 methylene blue method the procedure recommended by Eugling* from 

 experience in F. B. Hofmann's laboratory has been followed. 



This examination of the muscles has fully confirmed the previously 

 reported abundance of nerve-fibres distributed quite outside the region of 

 distribution of motor plates, and that of these fibres many pass into the 

 tendon of insertion and then recurve to end at junction of tendon with the 

 fleshy part of the muscle. 



The methylene blue preparations have given results agreeing with those 

 obtained by Huberf and by A. Dogiel.iJ: They show the whole region of the 

 musculo-tendinous junction of the muscle to contain a zone rich in nerve- 

 endings of obviously receptive (sensorial) type, extending as a band right 

 across the entire transverse breadth of the muscle (see figure). In addition to 

 these endorgans at tendon-muscle junction there are numbers of other nerve- 

 endings of various and evidently non-motor type scattered throughout the 

 muscles. Instances pf these have been classified and figured by Huber and 

 Dogiel.§ Our preparations confirm their description, and add little to it, 

 except that we find, especially in the monkey, numerous endings which we 

 incline to regard as receptive spindles (muscle-spindles) of peculiarly simple 

 form. 



Tendon Nerves. — In the normal eye-muscles it is usual by the osmic acid 



* 'Archiv. f. d. gesammt. Physiol.,' vol. 121, p. 279, 1908. 



t ' Journ. of Comparative Neurology,' May, 1900, vol. 10, No. 2. 



X ' Archiv f. mikroscop. Anatomie,' 1906, vol. 68. 



§ lUd. 



