164 ON THE DIGESTIVE SYSTEM OF BIRDS. 



known to occur in the alimentary canal of birds, of, for instance, the 

 peculiar proventriculus and caeca of Chauna (though Dr. Crisp's paper 

 on this bird is quoted), and of the extraordinary stomachs of the species 

 of: Plotus. Xo allusion is made to the tongue of Nestor ; and the old 

 statements as to the universal absence of a gall-bladder, or, at all events, 

 its only exceptional presence as an individual variety, in the Parrots and 

 Pigeons, are repeated. 



In the second part Dr. Gadow commences with the different forms of 

 the same organs throughout the series of birds. In a tabular statement 

 of the correlation of the nature of the caeca to the nature of the food, 

 Phcenicopterus is included as one of the " Eleisch u. Fische " eaters. 

 But, according to Mr. Salvin and other authorities, the major part of the 

 food of these birds consists of the vegetable matter that grows at the 

 bottom of the lagoons which they frequent (vide Dresser, B. of Eur. 

 pts. 75, 76). The length and width of the alimentary canal, the relative 

 size of its various parts, the influence of the food on the canal as a 

 whole, and the variations in its length in birds of the same species, both 

 young and old, are then discussed. The concluding part of the paper is 

 devoted to a description of the disposition of the convolutions of the 

 intestines ; and this is decidedly the most novel part of Dr. Gadovv's 

 work, previous accounts of this subject being very meagre. 



Ibis, 1880, Excluding the Ratita?, Dr. Gadow distinguishes three chief types of 

 p. 236. intestinal arrangement. These he calls Orthoccela, Plagioccela (or Plagio- 

 brochi\ and Cycloccela. 



In the first group (Orthoccelci), in which, he includes the Pygopodes, 

 Steganopodes, Anseres, Tubinares, Erodii, Alectorides, and Rallida?, the 

 chief folds, which are from five to eight in number, are straight and 

 parallel to one another and to the long axis of the body. 



In the Plagiocoela, which includes only the Easores, the two middle of 

 the four chief folds form more or less horseshoe-shaped loops at their 

 extremities, and the general direction of the intestines always forms, 

 more or less, an angle with the long axis of the body. 



In the Cycloccela one or more of the chief folds are spirally coiled 

 round their ends. This division includes some of the Grallse, the 

 Pelargi, Laridae, Psittaci, Raptores, Columbae, the Coccygomorphae and 

 Pici in part, the Cypselomorphae, and the Passeres. 



It is further subdivided into the Telogyri, in which only the terminal 

 part of the fold is coiled, and the Hologyri, in which the whole fold is so 

 disposed, these latter, again, being further divided into Progyri, Mesogyri, 

 Amphigyri, and Polygyri. 



But, judging from the forms associated together under some of these 

 heads, the groups so named are eminently artificial. Thus, the Eaptores 

 are divided amongst the first three, and under the Mesogyri are included 

 forms as various as Astur, Melierax, Halcyon, and Phcenicopterus. 



