160 SPECIAL HISTOLOGY. 



Anatomy/ June, 1849; A. Ecker, ' Ueber die Veranderungen, 

 welche die Blutkorperchen in der Milz erleiden/ in s Zeitsch. 

 fiir Rat. Medicin/ VI, 1847, and art. f Blutgefassdriisen/ in 

 R.Wagner's < Handw. der Phys./ IV, 1, 1849; J. Landis, 

 f Beitrage zur Lehre iiber die Verrichtungen der Milz/ Zurich, 

 1847 ; Gerlach, ' LTeber die Blutkorperchen haltenden Zellen 

 der Milz/ in 'Zeitschrift fiir Rat. Medicin/ VII, 1848; 

 ( Gewebelehre/ p. 218 ; R. Sanders, ' On the structure of the 

 Spleen/ in Goodsir's 'Annals of Anat./ I, 1850; O. Funke, 

 f De sanguine venae lienalis/ Lips., 1851. 



[Gray, ' On the Development of the Ductless Glands in the 

 Chick/ < Phil. Trans./ 1852.— Eds.J 



OF THE RESPIRATORY ORGANS. 



§171. 



Under the head of respiratory organs are usually enumerated 

 only the larynx, trachea, and lungs ; but I consider it as most 

 suitable here to describe two organs connected genetically with 

 those respiratory organs of the embryo, which remain unde- 

 veloped, that is to say, the branchial arches ; and which, phy- 

 siologically, perhaps, belong to the lungs — the thyroid gland 

 and the thymus. 



OE THE LUNGS. 



§ 172. 



The structure of the lungs corresponds, in all respects, with 

 that of a compound racemose gland, presenting, in the lobes, 

 lobules, and air-cells, the proper glandular parenchyma ; whilst 

 the bronchia, trachea, and larynx, constitute the excretory 

 apparatus. They differ from common glands in this, that 

 since in the lungs a double process — an excretion and an 

 absorption of matters — is carried on, which affects the 

 whole mass of blood, the cavities are proportionately more 

 capacious, and also, on account of the special nature of their 



