CHAP. XIII.] DIGESTION IX FISHES. 473 



present in smaller proportion than in the other organs. He disco- 

 vered, however, a very small quantity of ' sinistrin,' a dextrin-like 

 carbohydrate first described by Schmiedeberg 1 as present in the 

 bulb of squill (Urginea scilld), which does not yield a sugar when 

 digested with diastase, but when boiled with dilute sulphuric acid 

 yields laevulose and an inactive sugar. 



SECT. 3. SOME PECULIARITIES OF THE DIGESTIVE PROCESS 



IN FISHES. 



In fishes, the salivary glands are either absent or rudimentary, 

 though Krukenberg found 2 that the buccal mucous membrane of the 

 carp and of Lophius piscatorius secreted a fluid possessed of diastatic 

 activity. The stomach secretes a very active gastric juice which was 

 supposed (like that of the frog) to contain a pepsin somewhat differing 

 from that of warm-blooded animals, in that it possessed digestive 

 activity at a temperature of C. 3 The experiments of Krukenberg 

 and of Max. Flaum 4 have shewn, however, that the ability to effect 

 proteolysis at C. is connected with the presence of a large quantity 

 of pepsin, and does not imply a difference between the pepsin of 

 warm- and cold-blooded animals. 



The striking peculiarity of a large number of fishes is the absence 

 of a definite pancreas ; in many of these there exist, however, the 

 so-called appendices pyloricce, caecal tubes connected with the pyloric 

 portion of the mid-gut, obviously the homologues of the mid-gut 

 gland of Mollusca, and discharging the same function, and in some 

 fishes so held together by connective tissue and united at a common 

 efferent duct as to have the appearance of a compact gland 5 . There 

 are fishes, however, in which both pancreas and appendices pyloricce are 

 absent; in these cases the mucous membrane of the mid-gut secretes a 

 juice which is possessed of diastatic and proteolytic (trypsin) activities 6 . 



SECT. 4. SOME PECULIARITIES OF THE DIGESTION OF BIRDS. 



" In the fore-gut of Birds there is a great division of labour. The 

 influence of adaptation to the mode of life, and more especially to the 

 mode of nutrition, is most clearly shewn by the variations in the 

 different arrangements. The oesophagus, which is of the same length 

 as the neck, is either of equal calibre along its whole course, or is 



1 0. Schmiedeberg, 'Ueber ein neues Kohlenhydrat,' Zeitsch, f. phys. Client. 

 Vol. in. pp. 112133. 



2 Krukenberg, op. cit. p. 67. 



3 Fick and Murisier, ' Ueber das Magenferment kaltbliitiger Thiere,' Arb. a. d. 

 physiol. Lab. d. Wiirzburger Hochschule, 1872, p. 181. 



4 Maximilian Flaum, 'Ueber den Einfluss niedriger Temperaturen auf die Func- 

 tionen des Magens' (Aus d. pbysiolog. Inst. d. Universitat Bern), Zeitsch. f. Biologie, 

 1892, pp. 433449. 



5 Gegenbaur, op. cit. p. 560. 



6 Ralpb Blanchard, ' Sur les fonctions des appendices pyloriques,' Comptes Rendus, 

 Vol. xcvi. (1883), p. 1241. 



