On a Non-striped Muscle of tlie Orbit, 323 



fibrous membrane which completes the cavity of the orbit as 

 entirely composed of white inextensile fibres. Gurlt* con- 

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

 fibres interpolated. H. Miiller, t in a very brief communica- 

 tion, states that he has found flat muscular fibres in the 

 inferior orbital fissure in man, and corresponding 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 

 repro traded in those animals which retracted the ball, 

 through the contraction of a retractor muscle. H. Miiller, 

 again, who speaks more positively than any who have pre- 

 ceded him, not only of the existence of a muscle, but also 

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

 it antagonises those muscles which retract the eye-ball into 

 the socket, and that thus, the reprotrusion of the globe is 

 produced, not by a mere elastic recoil but by a muscular 

 contraction. 



If this hypothesis be correct, an arrangement exists in 

 this locality which is certainly to be regarded as an unusual 

 one, — viz., an involuntary muscle acting as a direct anta- 

 gonist to a voluntary muscle. Whether the hypothesis be 

 correct, or not, I am disposed to consider that the muscle 

 has some especial relation to the vascular 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. 



Note. — Since the above paper was in type, my attention 

 has been directed, by Professor Huxley, to a communication 

 by H. Miiller, dated Dec. 15th, 1860, entitled "On the 

 Influence of the Sympathetic upon some Muscles, and on the 



* Handbnch der Vergleicli, Anat. der Hans. Saugethiere, 1860, p. 733. 

 t Siebold and Kolliker's Zeitschrift, 1858, p. 541. 



