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 branches 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. 
