584 SPECIAL HISTOLOGY. 



the first inspiration, O-Oo-OO-l-O-OG of a line ; the latter, at this time, 

 appear to exist in the same number as in the adult, the further increase 

 of the lungs proceeding only from the expansion of all its parts. 



[The pathological changes occurring in the tissue of the lung are 

 numerous. An atrophy of the parenchyma takes place in old age and 

 in emphysema. In the former, a thinning of the walls of the air-cells, 

 and a partial obliteration of the capillaries exists. In emphysema the 

 alveoli of the cells are enlarged, but the walls much attenuated; some- 

 times their rupture ensues and a communication between the sepa- 

 rate cells is established. Hypertrophy of the air-cells, with ejilarge- 

 ment of the capillaries, is observed in the hypertrophy of the lung 

 which occurs from increased functional action. Obliteration of the air- 

 cells is mostly caused by exudation or deposit into the air-vesicles or 

 the interstitial tissue. In pneumonia this exudation occurs mainly 

 into the alveoli, sometimes, however, into the walls of the cell, the 

 interstitial, or even into the interlobular tissue (interlobular pneumonia). 

 The granular appearance of red hepatization is owing to a complete ex- 

 pansion of the air-cells by the plastic exudation. In gray hepatization 

 the walls of the cells and the interstitial tissue become softened, and 

 undergo a fatty metamorphosis. 



Deposits of pigment occur as a consequence of hepatization, or from 

 a simple congestion of the lung. The pigment is found in the inter- 

 stitial tissue, and sometimes exists in sufficient quantity to compress 

 the air-vesicles and produce their atrophy. It is formed either from 

 the coloring matter of the blood, or else by the blood corpuscles break- 

 ing up into distinct pigment-cells and granules (Yirchow). Tubercle 

 is most generally deposited in the air-cells ; cancer more frequently in 

 the interstitial tissue. 



Effusions of serum, or of blood, occur either into the interstitial 

 tissue, or into the air-vesicles. In oedema the effused serum has its 

 seat in the air-cells, whilst in apoplexy of the lung, the blood is effused 

 in the interstitial tissue. A. fatty degeneration of the epithelial cells is 

 observed in portions of lung, compressed by a pleuritic effusion, in ate- 

 lectasis (Reinhardt), and in splenization. Accidental formations (bone, 

 cartilage) and cysts have their seats generally in the interstitial tissue. 

 Destruction of the parenchyma of the lung is the result of inflammation, 

 gangrene, tubercle, or cancer. A microscopical examination of the de- 

 stroyed parts shows them to be infiltrated with fine fatty molecules; the 

 elastic elements of the air-cells are generally found well preserved. DaC.] 



The investigation of the lungs presents no real difficulty, except in 

 one point ; that is, with respect to the relation of the pulmonary cells 

 to the terminations of the bronchice, but here the difficulties are very 



