140 DIGESTIVE SVSTEM 
arbitrary expressions ; but, if we assume that a relative length not 
exceeding 5 indicates a short, and one of more than 8 a long gut, 
we find that the Intestinal Canal is very short in all purely frugi- 
vorous and insectivorous birds, while it is very long in those which 
live upon fishes, carrion, grain, and grass. It must, however, be 
remarked that, according to the nature of the food, a short intes- 
tinal canal is often compensated by its width either wholly or in 
part, as of the rectum, or by the presence of large czca. Conse- 
quently all these points have to be considered in using the features 
of the intestine for taxonomic purposes. Ceteris paribus, the rela- 
tive length of the-canal is as good a character as many others, and 
occasionally by it alone closely-allied species can be determined. 
The subjoined table shews the measurements of the intestine in a 
few forms; but for fuller information the reader may be referred 
to (Bronn’s) Kl. & Ordn. Thier-R. Vogel, pp. 590-661 and 700, where 
the respective measurements of nearly 400 birds will be found. 
Absolute Length Length of 
of Intestinal Canal. 
1 Cecum.|{ Rectum. | Absolute , Relative 
cm. cm. em. 
Struthiocamelus . .. . 70 820 1430 20 
Casuariusindicus . . . . 3 28 180 3-4 
Spheniscus minor . a. 8 2 a 223 16 
Anser cinereus, var. dom. . 24 18 260 1, 
Procellaria leachi . Oe? 1°5 29 5 
Ardea cinerea cane 05 10 OA 10 
Gallus bankiva, va7. dom. 17-20 S511 | 186-170 8-10 
Syrrhaptes paradoxus. 12 10 80 ) 
Columba livia, var. dom. 0°8 4 108-182 | 11-13 
Pandion haliaetus . 0°3 9 300 18 
Astur palumbarius. 07 7 108 6 
Corythaix persa. 0 — 42 3-4 
Cypselus apus 0 — 17 3 
Corvus corax 1°4 5 120 8 
Manucodia atra. 0°5 3 29 2-3 
Passer domesticus . 0:2 2 Pal 5-6 
In early embryonic stages the Intestinal Canal is a straight 
tube ; but, as its growth proceeds far more rapidly than that of the 
body-cavity, it is necessarily thrown into folds or loops. Moreover, 
since it is suspended from the vertebral column by the mesentery, or 
lining of the body-cavity, its several folds are thereby connected 
with one another in various ways, and their number and shape 
depend to a great extent upon the space available in the cavity, as 
well as upon the shape, size, and position of the stomach and 
neighbouring organs ; but the various ways in which the small in- 
testine is stowed away in different birds exhibit types so definite 
and constant that they cannot be considered accidental or meaning- 
less features. On the contrary, a somewhat exhaustive study of its 
