264 Dr. Burnett’s Reviews and Abstracts 
The thickness of the primitive bundles corresponds exactly to 
that of Crampton’s muscle. his muscular layer is less easily 
observed with the eyes of doves, hens, turkeys, geese, ducks and 
crows, owing to the greater number of pigment cells in the cho- 
roidea, and to the greater disposition of the primitive muscular 
bundles to split up into the fibrilla, which have a varicose aspect, 
and are almost exclusively seen in prepared specimens.’ 
As to the function of this muscular layer, Wittich remarks: 
“Its action would contract the choroidea, thereby diminishing its 
He then alludes to the well-known relations 0 
Crampton’s muscle and of the pecten ; in the same category with 
which belongs the muscular tissue in question. 
Wittich’s concluding remarks may well be quoted: “TI will 
here mention a circumstance which seems to me well worthy of 
especial attention in comparative anatomy, but which unfortunate- 
have been unable to follow out thoroughly. It is, that with 
muscle has been disputed by some anatomists (see Huck, Die 
Bewegung der Krystallense, Leipzig, 1841); but now, from the 
investigations of our author, which so completely confirm those 
Treviranus, Crampton, and Krohn, the case admits of little 
oubt. 
The striated, and therefore voluntary character of this whole 
system of muscular apparatus is especially worthy of note in con- 
nection with the eminently adaptive power it gives to the eyes of 
these animals. mers 
