MACALISTER—-ON PYLORIC APPENDAGES OF THE COMMON TROUT. 187 
stomach, as is well known, is bent into the form of an acute angle, and 
towards the intestine becomes thick and muscular, with a rugous mucous 
membrane, and with a bilaminar muscular coat. In the common Trout 
this does not form a special organ, but in the Gillaroo it constitutes a 
regular gizzard. The pyloric constriction is narrow, and has a well- 
defined sphincter; and below this commences the intestine, which is 
thicker above than inferiorly. On its lining membrane, which is in- 
_vested with cylinder epithelium, there are the openings of a large num- 
ber of pyloric ceeca—small round orifices, arranged irregularly, some 
quincuncially but usually with no definite order of arrangement. 
from three inches and a half to half an inch in length, are cylindrical, 
These czeca vary and end in blunted extremities. These are usually 
arranged in two clusters—an anterior set, five in number, directed 
towards the front or inferior surface of the flexure of the stomach; these 
are long and large, united together by folds of omental tissue contain- 
ing blood-vessels: the second series is much the larger in number, and 
consists of from twenty-nine to thirty-nine ceca, placed nearly parallel, 
and directed to the left side, in a double row, longest near to the 
pylorus, but narrowing towards the lower part of the duodenum: at 
the former end they attain the length of an inch and a half to three 
inches; at the latter, halfaninch. These are closely united together and 
to the intestine by an areolar web, and exhibit many blood-vessels. 
When each of these ceca is examined, it is found to consist of a hollow, 
rather thick-walled tube, thicker in coats at the fundus than the middle, 
and narrowing in calibre to the neck. When carefully examined, one 
of these ceca appears to consist of the following layers :—First, an ex- 
ternal areolar or serous lamina, covered with a ciliated tesselated epi- 
thelium; secondly, a fibrous and muscular coat, consisting of circular 
fibres ; thirdly, a submucous, which is very vascular, and underlies a thick 
layer of glandular or spheroidal epithelium: the fluid secreted by it is 
viscid, alkaline, and mucous; the epithelial layer is much thicker at the 
fundus than at the sides of the tube. This forms the simplest form of a 
true secreting gland—a cecal unbranched follicle of large size. Ina 
tube of this size one might expect to find racemose crypts communicating 
with the central canal, but I could see no trace of any apparatus but 
the very simplest, i. e. a series of large single czeca. The secretion of 
these follicles was alkaline, dense, tenacious, and exhibited needle- 
shaped crystals, resembling tyrosin. 
When we trace through the class of fishes these appendages, we find 
a very great variety of development, indicating that their uses are not 
constantly required in the exigencies of fish digestion. In Amphioxus 
and Myxine they are absent, as likewise they are in the Sole and Stic- 
kleback among higher fishes. A rudiment exists in Anarrhicus lupus. 
In the Halibut there is one, according to Bloch and Cuvier. Swammer- 
dam, however, figures and describes four, in his ‘‘ Obs. Anat. Coll. pri- 
vato Amstelod.,” tom. i1., p. 47, and Tab. 11. f. 1. Polyacanthus pos- 
sesses two, as also in the Plaice and Turbot. The Anabas scandens 
possesses three, as likewise does the common Perch; four in Cottus 
gobio ; five in Trigla cuculis ; six in Cottus quadricornis and Platyce- 
