of the Fishery Board for Scotland. 



33 



PART I. 



CHEMICAL INVESTIGATION OF THE DIGESTIVE 

 PEOCESSES IN FISHES. 



THE HERRING 



The herring used for this purpose were as * fresh ' as could be obtained, 

 they were taken off the Aberdeenshire coast, and were inshore or ' rock ' 

 herring. All of them contained ripe or nearly ripe milt or roe, as the 

 case might be. The best general description of the herring is given by 

 Professor Huxley in his lecture delivered at the National Fishery Exhi- 

 bition, Norwich, April 1881, and published in Nature of that year, p. 607. 

 An opening leads from the back part of the mouth between the gill 

 rakers into the gullet, which 1 passes back into a curious conical sac, 

 ' which is commonly termed the stomach, but which has more the char- 



* acter of a crop.' In the following experiments this sac is referred to as 

 the ' cardiac sac ' or crop, although as a matter of fact it possesses a struc- 

 ture analogous to the cardiac end of the mammalian stomach. This conical 

 sac is continued dowa wards into a long narrow funnel-like duct, which 

 curves backwards upon itself, and opens into the middle of the air-bladder. 

 This is the ' pneumatic duct.' 



' Coming off from the under side (near its upper end) of the sac, and 



* communicating with it by a narrow aperture, there is an elongated 

 ' tubular organ, the walls of which are so thick and muscular that it 

 f might almost be compared to a gizzard. It is directed forwards, and 

 1 opens by a narrow prominent aperture into the intestine, which runs 



* straight back to the vent. Attached to the commencement of the intes- 

 ' tine there is a score or more of larger and shorter tubular organs, which 

 4 are called the pyloric cseca. They open into the intestine, and their 

 ' apertures may be seen on one side of it, occupying an oval space, in the 

 ' middle of which they are arranged three in a row.' 



The thick muscular gizzard-like organ is for convenience referred to in 

 these experiments as the 'pyloric sac' or the stomach, although structurally 

 it closely resembles the pyloric end of the mammalian stomach, at least as 

 far as regards the epithelium covering it. A good description of the intes- 

 tinal canal of the herring, accompanied by a figure, is given in the Histoire 

 Naturelle des Poissons, by Cuvier and Valenciennes, vol. xx. Another 

 figure is given in Owen's Anatomy of Vertebrates, vol. i. p. 20 ; while 



G 



