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XI. — Upon a koj^-steiped Mi'scle coisTfECTED WITH THE Orbital 

 Periosteum of Majs^ and Mammals, and on the Musculus 

 Kerato-ceicoideus. By Wm. Turner, M.B. (Lond.), F.RS.E., 

 Senior Demonstrator of Anatomy, Uniyersity of Edinburgli.* 



"Whilst engaged in making a dissection, ia the hnman subject, 

 during the winter session of last year, of the superior maxillary, or 

 second division of the fifth cranial nerve, my attention was attracted 

 to a pale-reddish, soft, mass, filling up the narrow chink of the 

 spheno-maxillary fissure, and extending, from the sphenoidal fissure 

 in the sphenoid bone, to the infra-orbital canal in the superior maxil- 

 lary bone. It was evidently connected to the superior (ocular) as- 

 pect of the periosteum of the orbit, and it was pierced by the orbital 

 branch of the superior maxillary nerve, from which, as well as from 

 the ascending branches of the spheno-palatine ganglion, it appeared 

 to receive its supply of nerves.t It completely shut ofi" the superior 

 maxillary nerve, with its infra-orbital continuation, from the cavity 

 of the orbit. 



Since the period of making the above observation, I have availed 

 myself of several opportunities of examiniag the same region in other 

 subjects, and have constantly observed appearances, of a nature simi- 

 lar to those just described. The amount of the reddish mass and the 

 depth of its tint vai-ied slightly in difi'erent instances. Frequently, 

 it was so pale as scarcely to attract attention, which may perhaps be 

 the reason why it has so long been neglected by anatomists. AVhen 

 carefully examined with the nalved eye, or, still better, with a single 

 lens, it was seen to exhibit a fibi-ous appearance. A small portion 

 snipped ofi" with scissors, teazed out with needles, and placed on the 

 stage of the microscope, under a quarter inch objective, was observed 

 to ibe composed of pale, flattened, band-like fibres, having a faintly 

 granular aspect, and presenting indications of elongated nuclei at 

 iatervals. From these characters I had little doubt that the struc- 

 ture in question consisted of the non-striped form of muscular fibre. 



As considerable difficulty is alw^ays experienced in obtaining for 

 examination the contents of the hxnnan orbit, in a perfectly fresh 

 condition, I, in the next instance, proceeded to dissect the orbits of 

 some of the more readily obtained mammals, Avith a xiew of ascertain- 

 ing if a similar structure existed iu them. In the orbit of the sheej), 

 I have most satisfactorily observed appearances which have fidly con- 

 firmed the opinion of the structure already expressed. The orbit of 

 this animal difters from that of man in possessing much less perfect 

 walls. As a consequence of this, the orbital membrane, or periosteum, 

 is a structure of much impoi'tance, for it stretches across the floor of 



* Read before the Royal Physical Society of Edinburgh, Dec. 19th, 1861. 



t That jMcckel's ganghou sends brandies to the periosteum of tlic orbit is a fact 

 that has long been known to anatomists, though there have been difficulties in the 

 way of giving a satisfactory reason why such an arrangement prevails. The exis- 

 tence of the small muscle uow described, accounts for the distribution. 



