320 Proceedings of the Royal Physical Society. 



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

 maxillary bone. It was evidently connected to the superior 

 (ocular) aspect 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.* It completely shut off 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 examining the 

 same region in other subjects, and have constantly observed 

 appearances of a nature similar to those just described. 

 The amount of the reddish mass, and the depth of its tint, 

 varied slightly in different 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. 

 When carefully examined with the naked eye, or, still 

 better, with a single lens, it was seen to exhibit a fibrous 

 appearance. A small portion snipped off with scissors, 

 teased out with needles, and placed on the stage of the 

 microscope, under a quarter-inch objective, was observed to 

 be composed of pale, flattened, band-like fibres, having a 

 faintly granular aspect, and presenting indications of elon- 

 gated nuclei at intervals. From these characters I had 

 little doubt that the structure in question consisted of the 

 non-striped form of muscular fibre. 



As considerable difficulty is always experienced in obtain- 

 ing for examination the contents of the human orbit, in a 

 perfectly fresh condition, I, in the next instance, proceeded 

 to dissect the orbits of some of the more readily obtained 

 mammals, with a view of ascertaining if a similar structure 

 existed in them. In the orbit of the sheep, I have most 

 satisfactorily observed appearances which have fully con- 



* That Meckel's ganglion sends brandies to the periosteum of the 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 existence of the small muscle now described accounts for the distri- 

 bution. 



