108 ORIGINAL ARTICLES. 



derable quantity of a yellowish tissue, wliicli lie considers to be elastic, 

 interpolated with it. He regards the opinion, which had been previ- 

 ously advanced by GurJt, that the tissue was muscular, to be erroneous. 

 Stannius* states that in those animals, in which the bony wall of the 

 orbit is incomplete, the separation between the orbital cavity and the 

 temj^oral fossa is mostly effected by a fibrous membrane, containing 

 also abundant elastic tissue. He states that Sucloljjhi regarded these 

 elastic fibres to be muscular in Bears, and that Meckel described a 

 muscle in the orbital membrane of Ornithorynchus. Chauvemif 

 speaks of the fibrous membrane which completes the cavity of the 

 orbit as entirely composed of white inextensile fibres. GurltX con- 

 siders it to be a strong fibrous membrane, with yellow elastic fibres 

 interpolated. S. Ji£uUer,§ in a very brief communication, states that 

 he has found flat muscular fibres in the inferior orbital fissure in man, 

 and corresjD ending structures connected to the membrana orbitalis 

 of mammalia. 



It was supposed by those, who held that the membrana orbitalis 

 was a highly elastic and not a muscular structure, that it was through 

 its elastic recoil that the eye-ball was re-protruded in those animals 

 which retracted the ball through the contraction of a retractor 

 muscle. H. Muller, again, who speaks more positively than any who 

 have preceded him, not only of the existence of a muscle, but also 

 of the kind of fibre of which it is composed, considers that it antago- 

 nizes those muscles which retract the eye-ball into the socket, and 

 that thus, the rejjrotrusion of the globe is produced, not by a mere 

 elastic recoil but by a muscidar contraction. 



If this hypothesis be correct, an arrangement exists in this locality, 

 which is certainly to be regarded as an unusual one, viz. : an involun- 

 tary muscle acting as a direct antagonist to a vohmtary muscle. AVlie- 

 ther the hypothesis be correct, or not, I am disposed to consider that the 

 muscle has some especial relation to the vascidar arrangements in the 

 orbit. Its extension backwards to the foramina through which the 

 orbital vessels proceed, and with which it is in immediate relation, 

 and the very abundant vascular network found in connection with it, 

 point, I think, to some special relation between the muscle and the 

 vessels, a relation which is not at all inconsistent with what is known 

 of the function of non-striped muscle in other localities. 



Occurrence of the Musculus lyerato-cricoidews. — In a paper, 

 entitled " Remarks on the Musculus Kerato-cricoideus (Merkel's 

 muscle)," published in the Edinburgh Medical Journal, February, 

 1860, I directed attention to an account, which had been given 

 by Dr. Carl Merkel of Leipsic (Stimm und Sprach-Organ, 1857), 

 of a hitherto imdescribed muscle of the humau larynx. Merkel 

 described this muscle as arising from the posterior surface of the 

 cricoid cartilage, and extending obliquely upwards and outwards to 



• Lehrbuch der verglcichenden Anatomic, 1846, p. 401. 



•f Traite d' Anatomic Comparee, 18.57, p. 753. 



j Handbuch der Vcrgleicli. Auat. der Haus. Saugethierc. 1860, p. 733. 



§ Siebold and Kollikers Zcitschrift, 1858, p. 541. 



