ALIMENTARY CANAL 23 



The intestine of birds varies much in proportional as well 

 as (naturally) in actual length. In the systematic part of 

 this work a number of actual measurements will be found ; 

 from these it is obvious that on the whole purely frugivorous 

 birds have a short gut, while fish- and grain-eating birds have 

 a long gut. To compare, for example, two birds of roughly 

 the same size but of different feeding habits, the touraco 

 and the common pigeon, we find in the former a gut of 

 42 cm., and in the latter of 108-132 cm. As the gut is 

 always longer than the abdominal cavity in which it lies, it 

 has to be thrown into folds in order to find room. 



In the embryo chick the gut is straight and is supported 

 by a continuous dorsal mesentery of equal vertical diameter 

 throughout. The coiling is both lateral, which results in 

 lateral foldings of the mesentery, and vertical, which results 

 in unequal growths of the mesentery. It only affects the 

 middle part of the alimentary tract, the oesophagus and 

 stomach on the one hand, and the rectum on the other, or 

 at least a part of it, retaining the original straight condition. 

 The lateral foldings give rise to secondary connections 

 between different regions of the mesentery, and tend to 

 obscure the course of the gut ; but it is easy, by carefully 

 removing the entire intestine to distinguish these secondary 

 mesenteries from the primary sheet binding the gut to the 

 dorsal body wall. 



When the body walls of a series of birds are removed, and 

 the disposition of the intestines thus shown examined, they 

 have been found to present great differences. These have 

 been studied and described by Gadow in two memoirs,' and 

 the main results extracted for the account of the digestive 

 system in Newton's ' Dictionary of Birds.' It is mainly 

 from the latter work that the abstract here given is drawn. 



In a goose, for example, the main disposition of the 

 intestinal folds is in a longitudinal direction ; they run ' 

 parallel with each other in a direction roughly coinciding 



■ ' Versuoh einer vergleichenden Anatomie des Verdauungasystemes der 

 Vogel,' Jen. Zeitschr. xiii. 1879, pp. 92, 339 ; ' On the Taxonomic Value of the 

 Intestinal Convolutions in Birds,' P. Z. S. 1889, p. 303. 



