358 MESSRS. GARROD AND DARWIN ON AN OSTRICH [Mar. 5, 



of those bones ; and they never showed any tendency to unite or 

 cross one another. They were thickly covered by the anterior cer- 

 vical muscles, and sent off symmetrical branches *. 



Superficially on each side of the neck ran a vein with the pneu- 

 mogastric nerve ; but that on the left side was not bigger than a 

 crow-quill, while that on the right had a diameter at the lower part 

 of the neck of two thirds of an inch. This condition is constant in 

 many birds. 



This right (practically the only) jugular vein, after coursing about 

 half or a little more up the neck, sent two branches to the head, 

 the second running in the middle line, just behind the trachea and 

 in front of the oesophagus, the first being a direct continuation of the 

 main trunk. 



The intestinal canal was 34 feet long ; and the two caeca, each 

 2 feet long and arranged like a spirally twisted cone, were situ- 

 ated 1 1 feet from the pylorus, which is very different from their 

 situation in most birds, as has been noticed by Owen. 



The diaphragm was well marked. It formed a partition which 

 divided the thoracic cavity into two parts, one posterior and small 

 containing the lungs, and the other anterior and large containing the 

 heart and liver. It was a fibrous membrane, concave forwards, with 

 a muscular attachment at either side to the ribs and intercostal 

 tissues, which it joined in about the middle of their course. This 

 muscular part was formed of transverse fibres in the middle and 

 upper part of the chest, while the lower ones slanted slightly up- 

 wards as they coursed towards the median line. They were about 

 2 inches long, and formed a thin layer. The pleural cavity was 

 closed above and below by the fibrous diaphragm becoming blended 

 with the first and last ribs. 



The anterior thoracic cavity, which contained the pericardium- 

 coated heart in its upper part, entirely independent of the pleural 

 cavity, was divided into two by a dense fibrous membrane which 

 sprang from two vertebral crura, much as the human diaphragm, 

 and extended above the line to join the sternum, along the border 

 which articulated with the ribs, leaving the heart entirely in front of 

 it ; its concavity was directed downwards and forwards ; and it was 

 separated from the diaphragm proper by very large air-cells. The 

 oesophagus also ran in the interval ; but the aorta was included in the 

 pleural cavity, being clearly seen through the membrane of the dia- 

 phragm, along the median line, before its removal. 



The liver was completely separated from the abdominal cavity by a 

 fibrous membrane, so that when the included viscera had been re- 

 moved it was not at all brought into view. The mesentery was very 

 dense and strong, the vessels, especially the veins, being of large size. 



* The presence of two carotids in this bird, while there is only one in Rhea, 

 would require that they should be far separated in Nitzsch's classification of birds 

 according to the number of these vessels — the Ostrich being in his first class, with 

 a carotid from each main aortic branch, and the Rhea in the fourth class, with 

 only the left developed. See Nitzsch's ' Pterylographv ' (English edition). App. 

 p. 171. 



