TEE LUNGS. 



55] 



Nutrient vessels. — By this name is designated the divisions of the bronchia] 

 arteries and vei7is, the terminal ramifications of which anastomose with the capil- 

 laries of the pulmonary vessels at the ultimate bronchules. 



It is generally admitted that the 

 two arterial systems — bronchial and 

 pulmonary — are independent of each 

 other, and also of the general circu- 

 lation. Kiittner believes he has in 

 several ways demonstrated the exist- 

 ence of communications between 

 bronchial and pulmonary arterioles, 

 and between the latter and the sub- 

 pleural arterioles. 



Lymphatics. — These vessels are 

 divided into superficial and deep. The 

 first form a network beneath the 

 pleura ; the second exist in large 

 numbers around the lobules. They 

 mix and terminate in the bronchial 

 glands ; but before doing so, they 

 enter the small lymphatic masses dis- 

 seminated in the texture of the lung, 

 in the neighbourhood of the bronchi. 

 There are also interlobular lymphatics 

 which follow the ramifications of the 

 bronchi and pulmonary artery. (Lym- 

 phatics of very small size have been 

 described as commencing in the 

 alveolar spaces, on leaving which they gain a proper coat or internal tunic, and 

 are subsequently supplied with valves.) 



Nerves. —The nerves supplied to the tissue of the lung come from the same 

 source as those of the bronchial tubes — 

 the pneumogastric and great sympathetic 

 nerves. Their ramifications accompany 

 the pulmonary vessels and bronchi, 

 and they show small ganglia on their 

 course. 



Functions. — To know that the lung 

 is the seat of the absorption of oxygen 

 and the expulsion of carbonic acid from 

 the nutritive fluid — phenomena accom- 

 panied by the transformation of the dark 

 into red-coloured blood, and the cooling 

 of the venous blood — is the only authen- 

 tic fact necessary to remember with 

 regard to the functions of this organ. 

 It must be added that the operations 

 from which all these phenomena result, 



take place in the lung by the mediate contact of the atmosphere introduced 

 into the pulmonary alveoli during inspiration, with the blood traversing the walls 



INFUNDIBULA OF LUNG, WITH INTERVENING 

 TISSUES. 



a. Epithelium; b, elastic trabeculae; c, membranouB 

 wall, with fine elastic fibres. 



Fig. 331. 



ARRANGEMENT OP THE CAPILLARIES AROUND 

 THE INFUNDIBULA. 



