For ascertaining correctly the form of any stomach,- it was found
that it should not be distended at the time of the animal's death;
that it should be examined as early as may be after death; and that
its form is best shown by gently distending it with air.
For the purpose of examining its internal membrane, it should be inverted previous to inflation; by which means, the folds that are generally observable in that membrane wholly disappear, as they arise merely from its want of contractility, when Compared to the more elastic nature of the external coats.
The stomachs of which Mr. Home has given descriptions, accom- panied with drawings of most of them, are those of the turkey, cod, hare and rabbit; beaver and donnouse; the water rat, common rat and mouse; the horse and ass ; the kangaroo; the hog, pecan, and elephant; the mole; the stoat and armadillo; together With those of men and of dogs. The circumstances principally noticed in these descriptions are the extent to which the articular lining is carried; the appearance of the membrane that succeeds its termination; the situation and forms of any glands that are observable in the several parts of each stomach; and, more e ecially, a contraction which in some animals forms a permanent division of the last stomach into two parts, and even inrothers, as man, where no such division has been observed. Mr. Home is of opinion, that a similar, though partial, subdivision takes place during life by muscular contraction, as some traces of it may in general be detected after death, if the stomach be examined early and under favourable circumstances.
From the anatomical structure of the different stomachs described in the present and two preceding papers, Mr. Home is led to consider the functions belonging to the several parts of that organ.
The cuticular lining of the first, second, and third stomachs of ru- minants has occasioned them to be considered as mere reservoirs; but since they are supplied with secretions, he thinks that, like those in the crops of birds, they assist in softening the food and in pre- venting fermentation. It appears also, from Dr. Stevens’ 5 experi- ments, that even these have somewhat of a solvent power.
Mr. Home makes a remark that he thinks deserving of notice, re- specting the preparation of food in the first cavity; namely, that a certain quantity is always retained there, even though the animal has fasted for a whole week previous to its death.
The digestive process of ruminants he considers as very similar to what takes place in biIds with gizzards, who swallow the food with- out mastication. It is then sofiened in the crop; after which the gizzard, like the grinders of the ruminant, prepares it for solution and conversion into chyle.
This general resemblance having led him to a more minute comparison of their glandular structure, it was observed, that at the entrance into the gizzard there is a glandular zone that secretes the true gastric juice, having the power of dissolving the food. This solution, according to Mr. Home, is the second step in the process of digestion, and is effected in ruminants by the cardiac portion of the
