ß44 D»"- HANS GADOW, 



and Herons do not yet shoAv the excessive enlargenient. Their 

 fishdiet distends the yielding stomach, and this, like an overstrained 

 elastic bag, does ultimately retain the originally only temporary shape. 



The gizzard of the American Ostrich or Rhea is by far less 

 muscular than that of the African Ostrich. The gizzard of young 

 birds exhibits the usual furrow on its great curvature, but in the 

 adult this furrow and projection into the stomach has disappeared and 

 has given place to a round bag, produced by the weight of the pebblcs 

 which the Nandu takes up, although in a much sm aller quantity than 

 the Ostrich. These pebbles naturally bulge out the walls of the sto- 

 mach, were the latter is weakest. 



The measureraents of the stomachs of a young and an adult 

 Rhea americana are: 



aß in young 34 mm, in adult 70, i. e. increase about 2 fold. 



The extraordinary strength of the gizzard of the Ostrich does 

 not permit of a bulging out of any part of itself, and the excessive 

 aniount of stones, in aggregate bulk several times larger than the 

 whole gizzard, drags down the yielding proventricular wall and rotates 

 the gizzard. 



Considering the dead weight of about 5 — 7 Ibs. which the adult 

 Ostrich carries about without any apparent use, almost its whole Or- 

 ganisation must be affected to meet the greater expenditure of mus- 

 cular power which is necessitated by this ballast. 



# 

 7. The stomach of Tuhiiiares, 



The gizzard of most Petrels is small, roundish, flattened down 

 on the right and left side. It is strongly muscular in Procellaria 

 and Ossifraga^ softer and comparatively larger in Diomedea. The 

 proventriculus is many times more roomy than the gizzard, and is 

 very dilatable. In those species, which possess a strong gizzard, the 

 portion between the glandulär area of the proventriculus and the 

 gizzard forms a sac which, like in the Ostrich, extends dorsal- and 

 analwards from the gizzard. The latter is completely turned over in a 

 direction opposite to that in the Ostrich, the originally left speculum 

 looking directly ventral, thig right one towards the proventriculus or 

 the neck. The course of the pyloric portion of the duodenum indi- 

 cates the way in which the gizzard has been turned. 



