THE STURGEONS AND STURGEON INDUSTRIES. 
247 
The pyloric apparatus is so obviously a diverticulum of the intestine that it may 
very appropriately be considered at this point. Three very wide openings lead from 
the dextral and ventral sides of the upper end of the duodenum into the pyloric 
apparatus, showing that this organ, in its simplest embryonic form, must be regarded 
as a system of pyloric appendages, three in number. Further examination shows 
that the three primary pyloric diverticula have become divided at their terminations 
as development proceeded into a number of cmcal pouches after the manner of a com- 
pound, racemose gland. These branches of the original three diverticular, however, 
remain invested by a solid tunic of connective tissue dnd peritoneum, so that there is 
but little indication externally that the internal structure of the pyloric apparatus is 
that of a system of branching cmcal tubes. In the young animal this outer tunic of 
the pyloric apparatus though quite thick is not nearly so thick as in the adult. 
The attachment of the pyloric apparatus in the fully developed animal embraces 
about half the circumference of the duodenum. 
The expanded distal end of the pyloric apparatus is attached by fibrous cords 
(originally derived from the mesentery) to the posterior side of the terminal part of 
the stomach. The external form of the pyloric apparatus is that of an irregular len- 
ticular body, the longest diameter of which is autero-posterior, with a narrower trans- 
verse diameter. The long diameter of the pyloric apparatus in the young of 9 inches 
is three fourths of an inch, the short diameter one-half inch. The thickness of the organ 
in a vertical direction is about one-fourth inch in the young of the size mentioned above. 
It fits into and lies partly embedded in the first loop of the alimentary canal, formed, as 
above described, by the oesophagus, stomach, and upper end of the duodenum. Upon 
opening the body cavity the pyloric apparatus is one of the most conspicuous structures 
brought to view, as is shown in the accompanying figures 27, 52, and 53, which show 
its relations far better than can be done in a lengthy description. 
In young sturgeons, 9 inches long, just as the oesophagus begins to widen and pass 
into the stomach, and at a point about inches from the point where the gullet 
begins as a continuation of the pharynx, it gives off a very important dorsal divertic- 
ulum — the air-bladder. This organ communicates by way of a longitudinally widened, 
but short canal, known as the pneumatic duct, with the oesophagus, and is closed by a 
sphincter muscle, while muscular fibers radiate from the edges of the passage and 
traverse for a little distance the ventral walls of the air-bladder or pneumatocyst. 
The pneumatic duct joins the pneumatocyst at its anterior fourth. 
The whole air-bladder has a compressed, oval form as viewed from above, and its 
thin walls may be distended so as to fill nearly one-third of the body cavity. The 
convex dorsal wall of the air-bladder lies in direct apposition to the body- wall, little 
or no peritoneum intervening, while its lower convex face is covered by a peritoneal 
investment which is continuous in the median line with the mesentery and at the 
edges of the air-bladder with the inner serous covering of the muscular wall of the 
belly. The air-bladder extends for two-fifths of the length of the body cavity. Its 
walls are quite thin in the young, except at the entrance of the pneumatic duct; in the 
adult they are relatively somewhat thicker, while the coating of peritoneum and con- 
nective tissue is also thicker. In a large sturgeon the capacity of the air bladder 
would probably exceed 2 gallons; its walls are smooth, glistening white, and not vas- 
cular, thus contrasting markedly with the structure of the same organ in Lepidosteus, 
in which the highly vascular transverse trabeculse give to the organ the aspect of a 
rudimentary lung. 
