204 Anatomical Belations of the [^^'i^^i.^^J^iaff 
IV. — The Anatomical Belations of the Ciliary Muscle in Birds. 
I. In the Green-hreasted Pheasant. 
By Henry Lawson, M.D., F.R.M.S., Lecturer on Histology in 
St. Mary's Hospital. 
Plate XXX. (lower half). 
Some years since, while working at the physiological problem of the 
accommoclation-power of the eye, I was led to examine the anatomical 
relations of the ciliary muscle. The first specimens on which I made 
my observations were the eyes of mammals. But the results were 
extremely unsatisfactory, from the circumstance that in the mam- 
malian eye the muscle is composed of tissue of the non-striated 
class. Many histologists tell us that the recognition of this sort of 
muscular structure is easy enough ; and this is true within certain 
limits. It is not difficult to say that a given mass of tissue is non- 
striated muscular tissue. But when we are required to define 
within exact limits the distribution of this piece of tissue, we come 
to a very complex task. The fact is that the non-striated mus- 
cular fibre and the connective-tissue fibre pure and simple, are so 
very like each other in appearance, that when they come into con- 
nection with each other, as they must in the case of the mammalian 
ciliary muscle, it is next to impossible to say where the one com- 
mences or the other ends. 
To obviate this difficulty, I turned my attention to birds. 
EXPLANATION OF FIGUEES. 
The following letters refer in all the figures to the same structures, re- 
spectively: — Co., cornea; ci., ciliary muscle; scL, sclerotic; ch., choroid; c. t., 
connective tissue (loose) ; sh., sheath. 
Fig. 1 shows the relation of the parts as shown under a low power (2 inch). 
Here the whole muscle is seen in pear-shaped section, and connected 
with the choroid by loose connective fibres at the border of the iris, and 
more strongly with the choroid behind. 
„ 2 shows part of the section under a higher power (i inch). The connective 
tissue character of the connection with iris is well seen, also the manner 
in which the fibres of the ciliary muscle pass forwards and become 
inserted in the sheath. 
„ 3, also seen under -i- inch, shows the sclerotic with its irregular-shaped pig- 
ment cells, and the fibres of the ciliary muscle, arising from the sclerotic, 
and streaming obliquely forwards and inwards. 
„ 4, also seen under i inch, shows the posterior extremity of ciliary muscle, 
and its relations to sclerotic and choroid. The latter having been torn 
away from the sclerotic, has left the ends of the fibres which had passed 
into the choroid, and by its removal have been ruptured. 
„ 5, seen under -| inch. In this specimen the fibre was ruptured by drawuig 
the sheath towards the centre of the eye, and pushing sclerotic in the 
opi)osite direction. The general course of the muscular fibres is very 
clearly seen, and the loose suspensory fibres of the iris are also shown. 
