306 AN INTRODUCTION TO ZOOLOGY 



in which therefore two portions can be distinguished, a cystic 

 duct coming from the bladder, and a common bile duct after the 

 various hepatic ducts have joined it. 



The pancreas in Lepus is unlike that in Scylliwn or Rana, in 

 that it does not form one discrete solid mass. On the contrary 

 it takes the form of a number of scattered glandular nodules generally 

 distributed throughout the omentum of the duodenal loop. They 

 appear almost like little lumps of fat slightly tinged with pink and 

 are more closely aggregated towards the anterior end. Here the 

 pancreatic duct starts and thence runs backwards, receiving small 

 ducts from the various nodules to open into the distal loop of the 

 duodenum about three inches beyond the bend. 



While not actually forming part of the alimentary system we 

 find, as in the dogfish and frog, the spleen closely attached to the 

 stomach by a gastro-splenic omentum. It has the form of an 

 elongated strip of tissue of dark red colour lying in the cardiac 

 region of the stomach. 



A general outline of the digestive processes in a vertebrate 

 and the parts played therein by the various parts of the alimentary 

 canal have already been considered when dealing with the frog, so 

 that it is not necessary to repeat them again here. 



Respiratory System. 



As pointed out already the glottis, protected by the 

 epiglottis, lies on the floor of the pharynx ; it leads into a cavity, 

 the larynx, or organ of voice. The wall of the hollow is supported 

 by cartilages of which the first is termed the thyroid, and this takes 

 the form of a wide band incomplete dorsally. The second cartilage 

 is the cricoid which forms a complete loop, narrow ventrally and 

 broad dorsally. Articulating with the antero-dorsal edge of the 

 cricoid is a pair of small cartilages, the arytenoids. Stretching across 

 the laryngeal cavity dorso-ventrally are a pair of membranous 

 flaps strengthened by fibre-elastic ligaments ; these are termed the 

 vocal cords, since their vibrations produce the voice. They are 

 attached ventrally to the thyroid and dorsally to the cricoid 

 cartilages. The presence of a fairly long neck makes it impossible 

 for the larynx to lead directly into the lungs as in Rana, and 

 consequently we find a longish straight tube, the trachea or wind- 

 pipe, connecting the two. The trachea lies on the ventral side, of 

 the oesophagus between it and the skin of the neck. Through- 

 out the whole of its length it is strengthened by a series of 

 cartilaginous rings incomplete dorsally, which keep it open and 

 nevertheless allow for a certain amount of distention of the adjacent 

 oesophagus. It enters the thoracic cavity and passes dorsal to the 



