40 Anatomy, Physiology, and Pathology of the 
Fig. 6. 
a, The Omasum, cut open to show its folds, &c. 
hj The Opening communicating with the ReticuUim. c, Tlie Al)omasum, or true Digestive Stomach. 
d, The Villous Membrane of the Abomasum, which is also plicated. 
fig. 7, representing the stomachs of the calf with the vessels injected, 
will show that the omasum, b, receives a large quantity of blood — 
much more than can possibly be required to maintain the integrity 
of its structure, and, consequently, this must be sent for the pur- 
pose of secretion. We therefore regard the function of the 
organ to be that of effecting the retention of the food by its me- 
chanism, so that it may undergo a more complete maceration and 
softening by its secretion prior to entering tlie abomasum. The 
food, which has passed the three first stomachs, now enters the 
fourth, where it is subjected to the action of a particular solvent 
fluid called the gastric juice, by which it is converted into a 
chymous mass. This viscus, whicli is marked c in figs. 6 and 7, 
is commonly called the rennet, probably from the circumstance 
that the preserved fourth stomach of the calf is used to coagulate 
the milk in the making of cheese : a fact which is referrible to a 
chemical action of the acid of tlie gastric j uice upon the casein 
