274 
ALIMENTARY SYSTEM — THE (ESOPHAGUS. 
SfSJ/ 
Fig. oil. — ^’ariolls cells from 
the lesophaijus of I/cli.v ^ofnatia 
L.. highly magnilied (after Vogt 
and Vung). 
I’lie IIaHnatox34iii stain acts by outlining the basal plates and 
staining the edges of the structures generally, and is strengthened and 
assisted in emphasizing important details and more especially the 
cones, by the use of a saturated aqueous solution of Eosin, which 
should l)e used for five or ton minutes, after which deliydrate with 
absolute alcohol through cigarette paper and clear with oil of cedar, 
then arrange the object on the slide, diy off the clearing agent with 
cigarette paper, and put a drop of Canada balsam, preferably in Xylol, 
on the object, and then place the cover glass in its i)ositiou and com- 
plete by cementing. 
The (Esophagus 1 shall cany ; (/)ayai', to eat) or tlullet, is a 
ciliated tube of variable length, thickness, colour, and markings in 
the different s})ecies, and which, though 
sometimes tle.xuous and in Neritina even 
sinuous in character, usually has au almost 
direct course extending in the Castropoda 
from the i)harynx to the stomach, but iu the 
Pelecypoda originating at the oral orifice owing to the absence of 
jiharyngeal si)ecialization. Its limits are ill detined, due to the im- 
perceiitible change in its structure and 
cai)acity, the walls being very di.sten.sible 
owing to the longitudinal folds into which 
they are thrown. Interiorly it is lined 
with cylimlrical and j)artially glandular 
epithelium, and exteriorly by muscular 
layers, whose successive contractions im- 
pel the food onwards towards the stomach, 
before reaching which the tube may ex- 
pand to form one or more distinct enlarge- 
ments, separated by imjre or less definite 
constrictions, corre.sponding to and in- 
dicating division of function. 
The Crop, the most anterior of the 
(esophageal enlargements, acts as a kind 
of reservoir or i)reliminary receptacle for 
the ingested food, and is a large and fusiform thin-walled sac, often 
conspicuous by tbe colour of its contents, occupying the front of the 
visceral hump in the testaceous .species and tilling a considerable part 
of the bodj" cavity. The lining membrane resembles the msophagus 
Fig. 545. — Alimentary canal of 
Limmca ^^crcgi’a Mull., X 4, showing 
the relative positions of the crop, 
paired giz/ards, stomach, etc. 
b.h. buccal hulh ; c. crop ; g. paired 
gizzards ; st. stomach ; /. plecton ; 
rectum ; ic. oesophagus ; s.g. sali- 
vary glands. 
